Amel Ziani

Nabiha Azizi
email: azizi@labged.net

Didier Schwab
email: didier.schwab@imag.fr

Monther Aldwairi
email: monther.aldwairi@zu.ac.ae

Nassira Chekkai
email: n.chekkai@gmail.com

Djamel Zenakhra
email: dzenakhra@gmail.com

Soraya Cheriguene
email: cheriguene@labged.net

Recommender System Through Sentiment Analysis

Keywords: Recommender systems, Colaborative filtering, Sentiment analysis, Semi-supervised SVM (S3VM)

Customer product reviews play an important role in the customer's decision to purchase a product or use a service. Customer preferences and opinions are affected by other customers' reviews online, on blogs or over social networking platforms. We propose a multilingual recommender system based on sentiment analysis to help Algerian users decide on products, restaurants, movies and other services using online product reviews. The main goal of this work is to combine both recommendation system and sentiment analysis in order to generate the most accurate recommendations for users. Because both domains suffer from the lack of labeled data, to overcome that, this paper detects the opinions polarity score using the semisupervised SVM. The experimental results suggested very high precision and a recall of 100%. The results analysis evaluation provides interesting findings on the impact of integrating sentiment analysis into a recommendation technique based on collaborative filtering.

I. INTRODUCTION

The goal of a Recommender System (RS) is to generate meaningful recommendations to users about items or products that might be of interest to them. This new area of research is gaining more importance mainly due to the effects of widespread use of social media. Most of the existing systems and resources are tailored towards English or other European languages. Despite the fact that Arabic is currently among the top ten most used languages on the Internet, there are very few resources for Arabic recommender systems.

This work is primarily concerned with the task of recommending different products to Algerian customers based on other customers' opinions. We focus on the top four languages used in Algeria: Arabic, Algerian dialect, French and English. Opinions analysis is concerned with the feelings and emotions expressed in a text. It is developing rapidly today because of the widespread usage of web and social media to express very large number of opinions. Therefore, we built a polarity detection system that proven it efficiency in previous experimental works [START_REF] Ziani | Detection de polarité d'opinions dans les forums en langue arabe par fusion de plusieurs SVM[END_REF][START_REF] Ziani | Combining Random Sub Space Algorithm and Support Vector Machines Classifier for Arabic Opinions Analysis[END_REF][START_REF] Ziani | A New hybrid classification system for subjectivity detection[END_REF][START_REF] Ziani | Recommender system for sports articles based on Arabic opinions polarity detection with a hybrid approach RSS-SVM[END_REF]. This system transforms reviews texts into a numerical evaluation and feeds them into a recommendation system to implement a collaborative filtering.

Users' emotions are stated explicitly with a vote or implicitly with comments. Those comments are written in natural language with specific vocabulary. They have a polarity score to foresee the vote associated with this comment and make recommendations about items that may interest other customers.

The novelty of this work stems from combining the fields of sentiment analysis and recommendation using collaborative filtering to produce a unique and functioning recommender system. We propose to integrate a semi-supervised classification-based opinions analysis system into a multilingual recommendation system. Firstly, the process of opinions classification extracts the statistical features set such as: number of words, emotionalism, addressing, reflexivity...etc. Secondly, the resulting features vector will be the numerical representation of the review's text in the classification phase by the semi-supervised SVM. Finally, a polarity score is generated to compute the vote for the collaborative filtering of the recommendation phase.

The rest of this paper is organized as follows. Section 2 defines the recommendation systems techniques. Section 3 describes the semi-supervised support vector machine. Section 4 explains in details the description of all the phases of the proposed hybrid system. Section 5 presents the results of the experimental analysis and evaluation.

II. RECOMMENDATION SYSTEMS TECHNIQUES

A recommender system provides suggestions to users, in multiple contexts. For example, when choosing between multiple items or providing the customer with suggested products. Recommender systems are used in most e-commerce websites, where the system displays a list of recommended items to the end user. The core function of a recommender system is to identify potentially useful items for users [START_REF] Adomavicius | Toward the next generation of recommender systems: A survey of the state of the art and possible extensions[END_REF]. In order to predict these, a RS has to be able to predict the utility of these items. Then, based on the results, the system decides which items to recommend.

Recommender systems are commonly classified into three types according to how recommendations are made, namely: content-based filtering (CBF), collaborative filtering (CF), and social filtering (SF) systems. A CBF system suggests user items similar to those he preferred or liked in the past. A CF system suggests user items that people with similar preferences liked in the past while a SF system suggests items according to the preferences of the user's social contacts on social media network. Each of these types of recommendations has its own strengths and weaknesses. In order to address particular short comings and compensate for weaknesses, hybrid filtering (HF) systems combine different recommendation approaches.

III. SEMI-SUPERVISED SVM

Semi-supervised support vector machine (S3VM), proposed by Bennett and Demiriz [START_REF] Bennett | Semi-supervised support vector machines[END_REF], is a learning method based on cluster assumption. The optimal goal of S3VM is to build a classifier by using labeled and unlabeled data. Similar to SVM, S3VM requires the maximum margin to separate the labeled and unlabeled data. The new optimal classification boundary must satisfy that the classification on original unlabeled data has the smallest generalization error.

Ding et al. [START_REF] Ding | An overview on semi-supervised support vector machine[END_REF] explained that the S3VM can be used on all two-class problems in semi-supervised learning. Assuming that there is a dataset, A, with a total of one thousand sets, where one hundred sets are labeled, and the others are Only one hundred sets of data may be used with SVM. On the contrary, semi-supervised SVM can make full use of the one thousand sets. Additionally, the performance of semisupervised SVM is better than SVM. In conclusion, semisupervised SVM is the best choice, if there are small amounts of labeled data and large amounts of unlabeled data.

Semi-supervised support vector machines have been widely used in many classification problems [START_REF] Xiang | Improving twitter sentiment analysis with topicbased mixture modeling and semi-supervised training[END_REF][START_REF] Becker | Sentiment analysis on twitter with self-training and polarity lexicon expansion[END_REF][START_REF] Baugh | bwbaugh: Hierarchical sentiment analysis with partial selftraining[END_REF][START_REF] Liu | Cotraining and visualizing sentiment evolvement for tweet events[END_REF][START_REF] Tan | User-level sentiment analysis in corporating social networks[END_REF][START_REF] Pozzi | Enhance user-level sentiment analysis on microblogs with approval relations[END_REF][START_REF] Johnson | On classifying the political sentiment of tweets[END_REF][START_REF] Hong | Competitive self-training technique for sentiment analysis in mass social media[END_REF][START_REF] Drury | Guided self training for sentiment classification[END_REF][START_REF] Wan | Co-training for cross-lingual sentiment classification[END_REF][START_REF] Li | Semi-supervised learning for imbalanced sentiment classification[END_REF][START_REF] Yu | Exploring co-training strategies for opinion detection[END_REF][START_REF] Li | Employing personal /impersonal views in supervised and semi-supervised sentiment classification[END_REF]. Because of the lack of labeled Arabic or Algerian datasets we took advantage of the S3VM superior performance with unlabeled datasets.

IV. SYSTEM ARCHITECTURE

As explained earlier the system addresses two problems. First, constructing recommendation system for Algerian users based on opinions analysis. Second, dealing with the four languages, of Algerian users, including: Arabic, Algerian dialect, French and English. Fig. 1 summarizes the different phases of proposed solution.

Collaborative filtering

Breese et al. [START_REF] Breese | Empirical analysis of predictive algorithms for collaborative filtering[END_REF] divided collaborative filtering algorithms into two categories: memory-based algorithms [START_REF] Aggarwal | Horting hatches an egg: A new graph-theoretic approach to collaborative filtering[END_REF][START_REF] Herlocker | An algorithmic framework for performing collaborative filtering[END_REF][START_REF] Nakamura | Collaborative filtering using weighted majority prediction algorithms[END_REF][START_REF] Resnick | GroupLens: An Open Architecture for Collaborative Filtering of Netnews[END_REF][START_REF] Sarwar | Item based collaborative filtering recommendation algorithms[END_REF] and model-based algorithms [START_REF] Billsus | Learning collaborative information filters[END_REF][START_REF] Canny | Collaborative filtering with privacy via factor analysis[END_REF][START_REF] Chien | A Bayesian model for collaborative filtering[END_REF][START_REF] Getoor | Using probabilistic relational models for collaborative filtering[END_REF][START_REF] Goldberg | Eigentaste: A constant time collaborative filtering algorithm[END_REF][START_REF] Hofmann | Latent semantic models for collaborative filtering[END_REF][START_REF] Marlin | Modeling user rating profiles for collaborative filtering[END_REF][START_REF] Pavlov | Collaborative filtering with maximum entropy[END_REF][START_REF] Pennock | Collaborative filtering by personality diagnosis: A hybrid memory and model-based approach[END_REF][START_REF] Sarwar | Application of dimensionality reduction in recommender systems{a case study[END_REF][START_REF] Si | Flexible mixture model for collaborative filtering[END_REF][START_REF] Srebro | Weighted low-rank approximation[END_REF][START_REF] Ungar | Clustering methods for collaborative filtering[END_REF]. Memory-based algorithms compute a prediction by combining ratings of selected users or items that are judged to be relevant. Model-based algorithms use all available ratings to learn a model, which can then be used to predict the rating of any given item by any given user. Memory-based CF algorithms can be further divided into userbased CF algorithms and item-based CF algorithms.

In this work, we used the user-based CF algorithms [START_REF] Herlocker | An algorithmic framework for performing collaborative filtering[END_REF][START_REF] Resnick | GroupLens: An Open Architecture for Collaborative Filtering of Netnews[END_REF], where a set of k nearest neighbors of the target user is identified first by calculating the correlations or similarities between the users' ratings. We experimentally found that spearman similarity was the best similarity measure for the proposed system. Spearman similarity consists of finding a correlation coefficient, not between the values taken by the two variables, but between the ranks of these values. It is defined by:

𝑟 𝑠 = ∑ ((𝑟𝑎𝑛𝑔(𝑥 𝑖 -𝑟𝑎𝑛𝑔(𝑥) ̅̅̅̅̅̅̅̅̅̅̅ )(𝑟𝑎𝑛𝑔(𝑦 𝑖 -𝑟𝑎𝑛𝑔(𝑦) ̅̅̅̅̅̅̅̅̅̅̅ )) 𝑛 𝑖=1 √∑ ((𝑟𝑎𝑛𝑔(𝑥 𝑖 -𝑟𝑎𝑛𝑔(𝑥) ̅̅̅̅̅̅̅̅̅̅̅ ) 2 ∑ (𝑟𝑎𝑛𝑔(𝑦 𝑖 ) -𝑟𝑎𝑛𝑔(𝑦) ̅̅̅̅̅̅̅̅̅̅̅ ) 2 𝑛 𝑖=1 𝑛 𝑖=1 (1)
Where, (xi) and (yi) are the observation's ranks in the sample.

The similarities between the users range from -1 to 1. We chose the value 0 as a threshold to identify the closest neighbors of a user. The collaborative filtering with spearman similarity selects the items chosen by similar user's profiles. These last post reviews associated to their preference items.

Opinions analysis

Fig . 2. explains the architecture of the proposed sentiment analysis system. We start first by explaining the features extraction task. Then provide a short overview of the selected features and later we explain the classification phase using the semi-supervised SVM.

Reviews acquisition

Because the proposed recommender system is tailored towards Algerian users, we have collected a labeled corpus that comprises almost one thousand reviews in Arabic (MSA), one hundred in Algerian dialect and two thousand in French and English. We also have managed to collect one million unlabeled reviews by using a web crawler. The crawler is a web robot that systematically browses the World Wide Web, and is usually used for the purpose of web indexing.

The main motivation behind using the semi-supervised learning is to employ the large collection of unlabeled data jointly with a few labeled examples for improving generalization performance. Therefore, we have selected two thousand structured reviews for the training of the S3VM.

Features extraction

Feature extraction is a rudimentary and essential phase in Sentiment detection process. Therefore, it is important to convert the Arabic review text into a feature vector, so as to process text in a much efficient manner. The selected features used in our system for polarity detection can be summarized as follow. • Emotionalism: The researchers exploited the presence of the adverbs and adjectives in a document as an indicator permitting to determine the opinions. We calculated the emotionalism of a document by counting the number of the adverbs, adjectives and predicates.

Number of sentences = ∑ 𝑠𝑒𝑛𝑡𝑒𝑛𝑐𝑒𝑠

Emotionalism =

∑ 𝑃𝑟𝑒𝑑𝑖𝑐𝑎𝑡𝑒𝑠+∑ 𝐴𝑑𝑗𝑒𝑐𝑡𝑖𝑣𝑒𝑠+∑ 𝐴𝑑𝑣𝑒𝑟𝑏𝑠 ∑ 𝑛𝑜𝑢𝑛+∑ 𝑣𝑒𝑟𝑏𝑠 [START_REF] Drury | Guided self training for sentiment classification[END_REF] • Reflexivity: The reviewers used a lot of reflexivity pronouns such as: «I/me ,»أنا «I am personally شخصيا أنا », the use of »ي« in « ,رأيي I think that », « نظري وجهة من , my point of view »…etc, All of these sentences make reference to an opinion of review, and therefore, we include the measure of the reflexivity. All documents contain a large number of these words will be more subjective. This measure is expressed by Ref (d):

Ref(d) = |{𝑤∩𝑤 ′\ 𝑤∈𝑑,𝑤 ′ ∈𝑅}| |𝑅|+|𝐴| (17)
Where,

d

Classification

The Sentiment Polarity Classification is a binary classification task where an opinionated document is labeled with an overall positive or negative sentiment. Sentiment Polarity Classification can also be termed as a binary decision task. The input to the Sentiment Classifier can be opinionated or sometimes not. When given a review is as an input, analyzing and classifying that review, as a good or bad news, is considered to be a text categorization task. Furthermore, this piece of information can be good or bad news, but not necessarily subjective (i.e., without expressing the view of the author). What means this task is a multiclass categorization, where the review can be positive, negative or neutral. S3VM was chosen as the classification techniques for this phase, in order to benefit from all the collected dataset: labeled and unlabeled in the training.

Recommendation

Once the neighbors are obtained and their associated reviews are classified, a weighted average is used to combine the neighbor's item ratings to produce a prediction value for the target user. As soon as all the similarities of the target user A with respect to the other users are calculated using Spearman similarity (equation 1) and the n most similar users that constitute the vicinity of this target user are defined, the prediction (PAj) of the value of an item j evaluated by the user A is calculated using the weighted sum of the estimates of the nearest neighbors who have already estimated the item j as follows:

𝑃 𝐴𝑗 = 𝑣 𝐴 ̅̅̅ + ∑ 𝑠𝑖𝑚(𝐴, 𝑖) * (𝑣 𝑖,𝑗 -𝑣 𝑖 ̅) 𝑛 𝑖=1 ∑ |𝑠𝑖𝑚(𝐴, 𝑖)| 𝑛 𝑖=1 (19)
Where, n: number of users present in the neighborhood of A, having already voted on item j v𝑗, 𝑘: Vote of user for object j v𝑖: Average user rating i |sim (𝐴, 𝑖) |: Average Similarity

The latter value allows knowing if an item is relevant or not for the target user. This helps the system to generate efficient recommendations for that user. The global range of votes of a recommender system is represented by explicit votes that vary between 0 and 10, if the prediction value ranges between 0 and 5, the item will not be interesting for the user. While the values ranging between 5 and 10 correspond to relevant recommendations for this user.

IV. ANALYSIS OF RESULTS

The system performance has been evaluated with three measures: MeanAbsoluteError (MAE), precision and recall.

• The MeanAbsoluteError (MAE) is the most widely used measure in recommendation systems. It estimates the mean of the absolute difference between the and the predictions. The collaborative recommendation system is considered to be performing well when the MAE value is small. our system, the smaller the MAE, the more efficient the analysis of opinions. This measure is given by the following equation.

𝑀𝐴𝐸 = 1 𝑛 ∑|𝑓 𝑖 -𝑦 𝑖 | 𝑛 𝑖=1 (20)
Where, n is the predictions number, fi is the prediction of i, yi is the evaluation (vote)

• The precision which corresponds to the number of comments ranked well in relation to the total number of comments contained in the corpus. The collaborative recommendation system is considered to be performing when the value of the precision is high.

• The recall, known as sensitivity, is the number of related comments retrieved over the total number of relevant comments contained in the corpus.

In our system, the higher the precision, the more effective the opinions analysis system. Precision and recall are measured for each class as follows:

𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛 = 𝑇𝑃 𝑇𝑃 + 𝐹𝑃 (21) 𝑅𝑒𝑐𝑎𝑙𝑙 = 𝑇𝑃 𝑇𝑃 + 𝐹𝑁 (22)
To highlight the importance, and to clarify the effect of the combination between Arabic opinion classification and recommendation techniques, we carried out multiple experiments to calculate the previous measures. We have tested our approach using different datasets in multiple languages to confirm the efficiency of the proposed system. English dataset: is the Restaurant_TijuanaRestaurant dataset [START_REF] Zheng | [END_REF], which contains 2000 reviews from 50 guests in 40 restaurants. We chose this benchmark because it contains all the necessary information on which our contribution is based (comments and votes).

French dataset: collected from ldlc.com1 , "High-Tech Experience" online computer hardware sales website. Our dataset contains 10 users, 5 smart phones and 50 evaluations.

Arabic and dialect dataset: collected from dz.jumia.com2 , "JumiaMarket", which is an Algerian-based online shopping website. Our dataset consists of 10 users, 5 oriental clothing for women and 50 evaluations. precision and recall for the proposed system for the three datasets. We can safe say that our system has high precision and recall. That validates the use of S3VM and confirms that applying sentiment analysis techniques to recommendation systems significantly improves the quality of the recommendations. The system sensitivity in terms of recall was measured at 100% for the datasets. That maximizes the chances for a specific user to access the items he would like to have.

Our experiments validated our assumption of great advantages from combining: the opinions analysis and the recommender systems. Therefore, the new proposed hybrid approach significantly improved the recommendation system performance for Algerian users.

V. CONCLUSIONS AND FUTURE WORK

This study presented a basic tool which can be used to analyze Algerian reviews and comments and detect their polarity, in order to generate meaningful recommendations for users. To achieve this goal, we have tried to use semisupervised SVM for the opinions classification task to avoid the lack of annotated data problem. The obtained scores from S3VM were used as votes for the recommendation task. To prove the proposed combination efficiency, we have tested and evaluated our system using three datasets (Arabic, Dialect, French and English,). The results were very promising, which encouraged us to continue working along this line. Therefore, we intend to enrich our feature vector with another set of morphological primitives using natural language processing. We plan also to study the choice of using other recommendation techniques.

Fig. 1 .

 1 Fig. 1. The proposed process for recommendation system based on opinions analysis.

Fig

  Fig. 2. The proposed process for opinions analysis

  : document R: reflexivity list |R|: the number of reflexivity pronouns in d from R |A|: the number of addressing pronouns in d from A • Addressing: Most reviews contain some addressing words such as: « you ,أنت you ,انتم yourself ,نفسك yourselves ,أنفسكم he ,هو she ,هي them ,هم himself ,نفسه herself ,نفسها themselves ,»أنفسهم because the reviewers write their opinions addressed to others. Addressing list |R|: the number of reflexivity pronouns in d from R |A|: the number of addressing pronouns in d from A

  . 2. The proposed process for opinions analysis

					Features Vector
			Reviews Acquisition		1. Number of sentences 2. Number of positive words
	Collaborative Filtering	Using user-based algorithm (Spearman Similarity)			3. Number of negative words 4. Number of neutral words
			Features Extraction		5. Sum of polarity words
	Filtered Dataset				6. Average of positive polarity words 7. Average of negative polarity words
	Reviews Extraction		Classification (S3VM)		8. Average of neutral polarity words 9. Number of predicates
	(Opinions Dataset)				10. Number of Adjectives
					11. Number of Adverbs
	Opinions Analysis		Positive score		12. Average of predicates 13. Average of adjectives
	Polarity scores	Recommendation	Negative score	Neutral score	14. Average of adverbs 15. Emotionalism 16. Reflexivity
					17. Addressing

TABLE I

 I

	.	THE EXPERIMENTAL RESULTS
		MAE	Precision	Recall
	English	0.52	0.96	1.0
	French	0.50	1.0	1.0
	Arabic and dialect	0.60	0.90	1.0
	Table I. shows the results of our experiments. The table
	shows MAE,

http://www.ldlc.com/(17.06.2017)

https://dz.jumia.com/(17.06.2017)

ACKNOWLEDGEMENT This work was supported in part by Zayed University Research Office, Research Cluster Award # R17079.


General context of a dynami c agri cul tural sector in the Red River Delta Coll. General context of a dynamic agricultural sector in the Red River Delta

Thai Binh province contains a large population, of whom 93% are engaged in agricultural work. As livestock commodity chains are dominated by pork meat production, the swine breeding is intensifying rapidly and enjoys strong support from the local authorities.

Introduction

Northern Vietnam covers an area of 117,000 km 2 , or a little over one third of the country as a whole. It contains Hanoi, the political and administrative capital with more than 3 million in-habitants. From the north, a deep, mountainous hinterland opens out to the southeast onto the 15,000 km 2 of the Red River Delta. This wide, alluvial plain has one of the highest densities of rural population in the world, with 1,400 inhabitants per square kilometre and contains most of the population and the economic activity of Northern Vietnam. Recent history, despite the up-heavals suffered during the wars of the second half of the 20th century, has made it possible to equip the Delta with a considerable agricultural infrastructure, which has in turn greatly encouraged the rapid development of crop production. The Red River Delta is, after the Mekong Delta, the second-largest rice granary of Vietnam, itself the second-biggest exporter of rice in the world. Taking advantage of the country's liberalization in 1986 and its opening up to external markets, livestock production has also developed over the last ten years or so, responding to an increase in urban and foreign demand.

Thai Binh province is located 150 km southwest of Hanoi (Figure 1). It is bordered to the east by the South China Sea, to the west and south by the Red River (Sông Hông) and its tributary the Sông Trà Ly river, and to the north by the Sông Luôc and the Sông Hoá rivers. Divided administratively into eight districts, of which one is exclusively urban, it covers an area of about 1,500 km 2 . It contains a large population, of whom 93% are engaged in agricultural work. [START_REF]Bureau des Statistiques de Thai Binh[END_REF]. After the grim episodes of the famine of 1948, this province has always been noted for its rice production thanks in particular to colossal efforts in terms of irrigation. Livestock commodity chains are dominated by pig production. This porcine production is intensifying rapidly and enjoys strong support from the local authorities.

The socio-political environment and development policies

The various agrarian reforms

It is thanks to Ho Chi Minh, founding father of the Communist Party of Vietnam, that Vietnam liberated itself from French colonial rule. The country became officially free once again upon the Vietnamese declaration of independence in 1954. But many decades of conflict were neces-sary before Vietnam freed itself from the American presence. The war against the Americans officially ended in 1976. At that time, the communist political regime, already in power in Northern Vietnam, extended its control to the rest of the country.

After independence and the unification of the country, the Communist Party put a collectivization policy into place throughout Vietnam. In rural areas, land collectivization was enforced in two successive waves, in 1978-1979 and in 1983-1985.

From collectivized agriculture to Directive n°100 -With the installation of the communist government in Vietnam, the leaders choose to establish a collectivized agricultural system. But already in the '70s, this system is considered as bureaucratic and inefficient. It is paralysed by the State sector monopoly and planned allocations of subsidies [START_REF] Dao The | Changements récents de l'agriculture et défis du développement rural au Vietnam[END_REF]. With the reunification of the country in 1975 and the economy in the South being more developed, some co-operatives practise a system of informal contracts by which farmers can rent a given acreage of paddy fields in exchange for a set contribution. Directive n°100 in 1981 makes this system legal while leaving the cooperative in charge of decisions concerning crop planting. Most agricultural work becomes the responsibility of families who have to hand over part of their crops but can keep the rest.

The renewal marks the beginning of a policy change -In spite of the new boost given to agricultural production, the co-operatives suffer and their economic deficit deepens. The 6 th Congress of the Communist Party of Vietnam in 1986 then adopts the policy known as "Renewal" (Doi Moi), that marks Vietnam's commitment to a process of liberalization.

The acreage farmed by each co-operative member depends on its productive capacity and on the availability of co-operative land. Leases are for 20 years (rather than 1 to 3 years as before) during which the cooperative paddy fields are the farmers' responsibility.

Each co-operative member looks after a plot of paddy fields and is wholly responsible for the 8 stages of rice growing (formerly 5 stages). The rate of land rental is set at 10% for each crop and remains unchanged for 5 years. But in general, agricultural taxation is reduced. State farms enjoy financial autonomy. Should they go bankrupt, they are disbanded and their land divided up among farmers. Free trade is liberalized [START_REF] Liem | La nouvelle gestion des terres au Vietnam (1986-2000[END_REF].

As soon as it is declared law in 1987, this land regulation turns out to be difficult to enforce in the context of a market economy and a society in a state of rapid change, following the opening up of the Socialist Republic of Vietnam to non-socialist countries. On several occasions, the National Assembly passes amendment laws (1990, 1993 and 1999) accompanied by decisions and decrees for their enforcement. In 1999, the Prime Minister Pham Van Khai signs a decree by which the State recognizes (agricultural and urban) land use rights in accordance with the right of exchange, concession, rental, sub-rental, land use inheritance rights and the right to use land as security and as investment capital. However the enforcement of these laws remains difficult in practice and discourages farmers (3).

Bureaucratic malfunctions and price, salary and currency reforms led to the abolition of planned subsidies and of the dual pricing system (the market price and the state price). Resolution n°10 (Khoan 10) of 1988 recognizes the family farm as a production unit: it allocates agricultural land to family farms and abolishes the system of low-price compulsory sales and the policy of self-sufficiency for every district. This Resolution also had the effect of stopping State price control. In keeping with the principle that to achieve socialism, sufficiently rapid economic growth is at first necessary in order to be able to share it out equitably, the role of the market and the motivation of farmers are also taken into account. After twenty years of reforms, the Vietnamese economy has become liberalized and agricultural production has been developed. Currently, a clear differentiation is appearing between farms, and non-agricultural revenue is playing a large part in this. In the Red River Delta, 40% of farms have been in difficulties since the curtailment of the co-operative system. Although the reforms and socio-economic changes have positive consequences with regard to food security and development of agricultural production, the inequalities between farms are growing and the poorest ones are in an increasingly worrying situation.

This economic liberalization has led to Vietnam opening up to foreign markets. Vietnam is currently a candidate to join the World Trade Organization.

Thai Binh's development priorities

Since 2004, Thai Binh has declared its priorities to be the intensification of arable and livestock farming.

The directives concerning livestock development in the province over the period 2004-2010 aim to change the structure of agriculture, to industrialize agricultural production and to respond to market demands concerning livestock production. The People's Committee has concrete objectives: between now and 2010, it wishes to see, in Thai Binh province, the value of livestock production within agriculture totalling at least 40%. It also wishes to see the proportion of fattened cross-bred pigs with exotic breeds rise to 40% by 2010.

According to the provincial political powers, the two means of livestock production to be encouraged are "farms" and family farms, in order to reach 1.4 million pigs in 2010, with 1,600 livestock farms and 16,400 family farms. The transition from traditional livestock farming to industrial, or at the very least semi-industrial livestock production, would bring about an increase in the volume of production while improving quality and better responding to consumer demand.

The objectives of the People's Committee for the period 2004-2010 are therefore: to promote "industrial" livestock production (poultry and pigs), to industrialize the processing of livestock produce and to find marketing outlets.

In order to achieve these goals, technical progress in the production of breeding stock and in the processing industry needs to be made. To facilitate this, the government is trying to encourage livestock farmers, particularly with the help of financial subsidies, to adopt higher-return exotic breeds. The People's Committees place emphasis on training courses and extension activities to support farmers in the changes to their livestock farming systems. Finally, the Communal People's Committees are responsible for the construction of infrastructure in special areas, created to encourage the building of (semi-) industrial farms and family farms.

A densely populated environment intensively exploited by man

A large and dense population…

In 2002, there were 1,827,000 inhabitants in Thai Binh province, 94.2 % of them in a rural environment. The average population density is of 1,183 inhabitants per km 2 . The average num-ber of people per family is 3.75 and the population growth rate is 1.02%.

Vietnam is the most densely populated among Southeast Asia's major agro-economic countries. Average land area per capita is about 0.41 hectares, one of the lowest in the world. With a population density of 240 inhabitants km 2 with only 9 million hectares allocated for agriculture (i.e. one quarter of the total land area), the country has to support 9 inhabitants per ha of agricultural land (Table 2 and Table 3).

…but with low income

Agriculture remains fundamental to the Vietnamese economy, employing a labour force of 26 million (70% of active population) and contributing 24.3% of GDP in 2000 (Table 1). The country's approximately 10m ha of cultivated land is low compared with other countries of Southeast Asia (e.g. Thailand with 20m ha, Indonesia with 22m ha, Myanmar with 10m ha, and the Philippines with 9m ha). Vietnam's total food production in 2001 was about 34.5 million metric tons, of which 49% was from the Mekong Delta, 20% from the Red River Delta.

According to the Ministry of Agriculture and Rural Development, each farming household in Vietnam farms on average 7.5 sao (1 sao = 360 m 2 ) of paddy fields, giving two crops a year.

However, the plains of Northern Vietnam where Thai Binh province is located are overpopu-lated. There are about 800 to 900 inhabitants/km 2 of paddy fields. Each family farms 1.5 to 2 sao, which is equivalent to less than half the national average (3). The principal limiting factor in this province of Northern Vietnam is the drop in temperature from December to February, with a minimum temperature reaching 4 o C some years, which limits fish farming and prevents the growth of some species, such as rice.

b) Soil types

The national map of soil types only shows one type of soil for Thai Binh province. This is a soil derived from alluvia of the Red River, which flooded this region regularly until it was com-pletely confined, between the 13th and the 18th century. With its salty-clayey texture, this soil suitable for growing rice is reputed for its fertility (Table 3). In low-lying areas, the pH is often low, requiring farmers to lime their fields regularly (4).

There is also a second soil type (yellow alluvial soil), which is found on the alluvial terraces on either side of the Red River or its tributary the Trà Ly river. These terraces are flooded annually during the high water season, in July and August (Table 4).

These alluvial soils with low pH, about 6 (4), are the sign of a lack of alkaline reserves and of an environment low in carbonates that responds poorly to fertilization. They cover a small area, and are suitable for growing maize and groundnuts. In summer, the level in watercourses is high and the water carries a lot of alluvia down with it. The opposite occurs in winter, when salt water reaches from 15 to 20km inland.

A compartmentalized occupation of land

The agrarian landscape of the province is typified by a marked separation between inhabited and cultivated areas. There are three main agro-ecological units: i) Paddy fields i.e. diked-off land -on these wide plains, laid out with irrigated perimeters, the only dis-cernable "contours" are the dikes running along the main watercourses. This is an environment difficult to comprehend, as a difference in relative altitude between two plots of land of only a few tens of cm, often difficult to see with the naked eye, can cause significant differences in access to water and established crop types. Wherever one is, agricultural land is therefore classified according to its topographic level into ii) Alluvial land, flooded annually in July and August, has no access to irrigation. Dry crops are the first choice for this land, mostly maize, groundnuts and mulberry bushes [START_REF] Bahers | Diagnostic agraire dans le district de Hung Ha[END_REF].

iii) Inhabited areas are clearly defined and located on the highest ground; dwellings are in clusters.

Demographic pressure is such that within these areas, all available land surrounding houses is put to use. Living enclosures are thus places of multiple activities.

Agricultural production activities (fruit, vegetables, fish, pigs, etc.) as well as processing activities (crop drying, threshing, distilling rice alcohol, making soya tofu, etc.) can be found there, intermingled with domestic activities. The garden constitutes an important element of the family patrimony, in particular for historical reasons: during the collectivist regime, it was the only piece of land where families could grow what they wanted, and from which they could make a direct profit. It therefore appears in the Vietnamese land registry (Table 5).

Property title deeds have only recently been granted in Vietnam; it only happened in 1993 with the new land law, after a first stage that was carried out during the reform of 1986. These rights have a time limit on them: 20 years for land yielding annual crops and 50 years for land yielding perennial crops. Land was shared out according to pedological criteria, in particular soil quality, and topographical criteria, i.e. height of the land; but there is no link between the location of dwellings and family land.

The countryside is therefore typified by a spatial separation between dwellings, livestock farms and ponds on the one hand, and cultivated fields on the other. This is both a bonus and a constraint for the transfer of livestock effluents. Over the last few years, however, a transgression of this order has been witnessed; some livestock and/or fish farmers, constrained by the lack of available space on inhabited land and wishing to expand, set themselves up outside villages near paddy fields.

General context of a dynamic agricultural sector in the Red River Delta The importance of the hydraulic system Hydraulic constructions play an important part in the Delta's agriculture. For centuries, the inhabitants of the Delta have struggled against floods, in particular against those caused by the Red River, whose flow increases drastically during the rainy season. This struggle was given concrete expression by the construction of numerous primary and secondary dikes along the banks of the main rivers and their tributaries, in particular during the collectivist regime (from 1954 to 1986). At the same time, the need for water for crops initiated the establishment of a vast irrigation network, omnipresent in the rural landscape and primordial in the choice of crops to be planted. This is the case with growing rice, for which maintaining a permanent flow of water constitutes the prime means of controlling weeds. Almost all agricultural land can thus be irrigated and the paddy fields are crisscrossed with canals (often made of cement) and earth drains, potentially interchangeable thanks to motorized pumps or bailing.

Thai Binh province is one of the most recent deltas in the Red River drainage basin. It was formed by sea receding progressively to the east and by significant hydraulic constructions built in the past. The province can be thought of as an island that has been cut off, surrounded by the Red River, the Thai Binh River and the sea, with a very dense hydrographical network. Down-stream in the Delta, this province is located in the very low-lying area, where the topography varies on average from 1 to 2 metres. The water level follows the hydrological pattern of the Red River, the Thai Binh River and its branches downstream, as well as the tides. Flooding occurs in the summer season, from June to October, caused by excess rain and river water; the low-water level season lasts from November to May. The tide fluctuates between 1.9 to 2.4 metres on average, with a maximum of 3.8 metres.

The containment of the rivers has divided Thai Binh into two independent primary hydraulic ponders in terms of irrigation and drainage, separated by the Kien Giang River, namely: North and South Thai Binh (Table 6).

The Northern ponder of Thai Binh includes the following districts: Hung Ha, Dong Hung, Quynh Phu and Thai Thuy. The South ponder includes the districts Vu Thu, Kien Xuong, Tien Hai and the town of Thai Binh. These two ponders are mostly irrigated and drained by gravitational irrigation and/or by pumping, depending on water levels in the rivers and the tide. Gravitational irrigation using locks is only practised at times of low tide, at the beginning of the summer season, but rarely in the spring. Drainage by pumping is mostly carried out by the big central pumping stations, managed by the hydraulic companies. The very powerful pumps with an outflow from 1,000 m 3 /h to 4,000 m 3 /h irrigate and drain areas from 50 ha to a few hundred ha.

Surface waters of Thai Binh are irrigated either by local pumping stations managed by the communes, or by gravitation and/or by bailing. Local pumping stations are either stationary or mobile (boat, bicycle) and use electric or petrol-driven pumps, with a small outflow (320 m 3 /h to 1,200 m 3 /h).

Intensive vegetable production, dominated by rice cultivation

Since the land redistribution of 1993, the State allocates 1 sao (360 m2) per inhabitant to be fed. Most families opt for food security and grow rice on between 3 and 10 sao, whatever their agricultural and non-agricultural activities. The great majority of paddy fields therefore receive two crops of rice a year: spring rice from February to May-June, then summer rice from July to October-November. Control of water supply made possible by hydraulic developments, the introduction of varieties with a shorter life cycle and a reduction in the time land lies fallow between crops have enabled the progressive integration of a third annual crop. Maize, potatoes and sweet potatoes are most commonly planted (Figure 7).

V The dry winter crops are: sweet potato grown to feed pigs and potatoes reserved for human consumption. Soya, processed into tofu, and maize, mostly grown as animal feed, as well as vegetables, can be grown all year long. The vegetables, cooking potatoes and groundnuts, are grown for local markets and for export, jute and yellow nutsedge (Cyperus esculentus), grown to make mats, are sold into commodity chains.

Perennial crops such as mulberries or bonsais are less common [START_REF]Bureau des Statistiques de Thai Binh[END_REF]. When living space permits, a vegetable patch or an orchard can be planted there. The produce usually goes towards feeding the family, but can also be sold at local markets.

Some of this produce is processed on the farm. The rice is used to make rice wine and noodles. After distillation, the mash residue is a by-product that goes into the feed rations for pigs. Soya is turned into tofu. The watery residues generated by the processing of soya and rice are also consumed by pigs.

Chemical inputs are widely used by farmers in the Delta, and high yields are obtained: about 7 and 5.5 metric tonnes/ha for spring rice and maize, respectively [START_REF] Vu | Recommandations en fertilisation organique pour les principales cultures annuelles[END_REF]. The communal co-operatives market fertilizers and herbicides and organize extension meetings every season, often in partnership with their suppliers (private and semi-private industrial companies).

Figure 8: Leaf vegetables production in Vu Thu district

Box 1: Crop cycles

The crop cycles observed on fields are shown in the table. They depend on the altitude of the land in relation to the hydraulic infrastructure. In contrast to rice, which is flooded, several other crops are described as "dry crops". Low-lying land can only receive two rice cycles in the spring and in the summer. In winter, the saturation of the land that follows the rainy season and the rice harvest is such that it makes it impossible to grow anything. The land is left to lie fallow and can be grazed by cattle. High-and mid-level land can receive three crop cycles. The following crop rotations have been observed: -Three dry crop cycles: Vegetables-Vegetables-Vegetables, Maize-Soya-Maize, Soya-Vegetables-Maize, -Two rice cycles and one dry crop cycle: Rice-Rice-Potatoes, Rice-Rice-Sweet

potatoes, Rice-Rice-Vegetables, Rice-Rice-Maize, Rice-Rice-Soya, -Two dry crop cycles: Maize-Maize, nutsedge-nutsedge, Groundnuts-Maize, -Two rice cycles: the rice cycles vary with the varieties used; when the field receives three cycles, the summer rice is often a short-cycle rice.

General context of a dynamic agricultural sector in the Red River Delta

R R R R R R R R R R R R R R R R R R R W W W DC DC DC DC DC DC DC DC DC DC DC DC R R R R R R R R R
Caption: R: rice, DC: dry crops W: winter dry crops

Livestock production, a booming pork commodity chain

Livestock farming accounts for 30 % of agricultural production in Thai Binh province. Given a significant increase in the consumption of animal products linked to the industrial development of the country, the development of livestock productions, especially pig production, is today receiving very special attention and significant support from the government.

According to the assessment of the situation in the province 4 , livestock farming is developing faster than arable farming. This evolution is progressively changing the structure of agricultural production. Indeed, the value of livestock production represented about 18% of the total value of agricultural production in 1995 but easily reached 26% by 2003. Some farmers have begun to produce livestock with a high added value: pigs for lean meat, high quality poultry. Provincewide, there are more than 6,700 medium-and largescale livestock farms. This specialized kind of farm, semi-industrial or industrial, usually generates a higher than average profit for livestock farmers.

However, the rate of current livestock farming development in the province has not realized its potential in the opinion of the provincial People's Committee. The changes in structure and farming practices are indeed slow. Traditional livestock farming is still predominant. For the most part, the farms remain small and scattered, often located in villages, where people live. Farmers wishing to increase their pig production are thwarted by a lack of funds to invest, an absence of land on which to extend their buildings and limited technical know-how to manage an industrial-scale production, beginning with control of reproduction, feeding, sanitary safety, and culminating in slaughter.

Overview of the pig production sub-sector

A significant potential for development of pork commodity chains exists on the country's domestic market, given the growth of towns, more so since pork remains the meat most favoured by the Vietnamese. In addition to fresh meat, there is also a market for some processed products, mostly made by traditional methods. These are mainly local salted meat products.

In addition to this are export possibilities. At the national level, exports linked to livestock farming for the moment only concern pork: 34,000 metric tons were exported in 2001, of which 15,000 metric tons to Russia, 12,000 to Hong Kong, 5,000 to China / Laos and 2,000 to Malaysia.

In 2002, Thai Binh province alone exported 4,000 metric tons of pork meat to Hong Kong. The government wishes to increase these exports and to conquer new markets. However, the poor quality of Vietnamese pork, too fatty, and its high production costs penalize it on world markets. Consequently, this desire to export and to develop the sub-sector results in an imperative to improve the quality of the product (standards of hygiene, proportion of lean meat, etc.).

The government has therefore implemented measures to support and encourage the development of intensive pork production. Subsidies are allocated to livestock farmers buying batches of more than 6 exotic sows. Easier access to credit is arranged for intensive pig farming investment projects. Training courses are given in several communes in order to improve livestock farming performances and to encourage production of leaner animals (feeding practices, genetic choices).

The provincial decree Nº12-NQ-TU concerning the development of livestock farming for the period 2004-2010 has thus set an objective of increasing livestock production by 13% annually, in order to reach 1.4 million animals in 2010. The pork subsector is the largest in the meat sector, far ahead of poultry or cattle and water buffalo, since it alone represents roughly 75 % of total production. The proximity of centres for meat consumption (Hanoi) and for processing and export (Haiphong) has encouraged the boom in pork production in the province. By 2004, with more than one million animals counted 5 (Figure 10), the pig herd has grown on average by roughly 10 % annually since 1993 (Figure 9), rising steadily from 400,000 animals to about 1.1 million in ten years [START_REF]Bureau des Statistiques de Thai Binh[END_REF]. This development has come with deep structural changes and this trend should continue over the coming years, because the provincial authorities consider the increase in pork production as a priority. A few variations aside, the pig herd is distributed evenly throughout the province's districts. 5 Corresponds to the numbers of pigs on farms at the time of the survey and not to the number of pigs produced annually

Pig producers and their various breeding systems

Pig production is a traditional activity in the rural environment; pork is the second staple foodstuff after rice and its sale represents a significant source of income for a large majority of rural households [START_REF] Bergeret | Dynamiques comparées de trois filières dans le delta du fleuve Rouge: riz, porc, ail -Spécial Vietnam[END_REF]. It therefore concerns nearly all farming households who in this way put to use the by-products of their plant produce (2). There are several categories of producers, as shown in Table 12. The great majority of rural households practise traditional livestock farming (Nông Hô). These small-scale farmers have their farms buildings near their homes. Generalizing, it can be stated that all houses in the communes of Thai Binh keep at least a few pigs. Their production is mostly destined for home consumption or for sale through very short commodity chains (friends, neighbours, local market). Pork production is not a significant source of income for these households. Indeed, it is not practised with this in mind, since these families have other, more significant sources of income: agriculture, other livestock farming, trade, other work, etc. These farmers usually do not seek to expand their operations, either because pig farming is not a priority or because they do not have the necessary funds available.

"Farms" (trang trai) are differentiated by the use of a permanent exterior workforce and their more advanced technical nature, both with regard to feeding and to genetics. Many belong to the Thai Binh Livestock Farming Company, the former provincial cooperative privatized in 2004, and are usually farrow-tofinish pig farms with exotic sows of the breeds Large White and Landrace. As opposed to traditional and familial pig farms, they are often located outside areas of settlement, owing to the large area taken up by their buildings, impossible to integrate into villages. The big farms are intensive, integrated operations with several kinds of farming practised on a large scale, according to the VAC system. These farms are for the most part the result of a business enterprise and not the enlargement of pre-existing pig farms. This is why they are situated outside villages, distant from where people live. The owners of these farms are often entrepreneurs who have invested heavily in them. Most seek to improve performance and to enlarge their farms.

Medium-sized farms in the process of intensifying production or family farms include a whole range of intermediary situations. In most cases, they have developed from small operations located in villages. Pig husbandry for the most part takes place on land also used for dwellings.

While reliable statistical data for farms remain rare, a survey of a sample of pig farmers made it possible the describe the main kinds of systems for managing existing herds in the province [START_REF] Emonet-Denand | Typologie fonctionnelle des exploitations porcines de la Province de Thai Binh basée sur le risque environnemental généré par les effluents d'élevages porcins[END_REF]. Fattening time and the final weight of pigs fattened for meat are variable. In Vietnam, a difference is made between "thit" pigs and "got" pigs. In theory, "thit" pigs are pigs being fattened and finished for meat, and "got" pigs are weaned piglets. In reality, all pigs destined for slaughter at a high weight (between 50 and 90 kg according to provinces breeds) are considered to be "thit" pigs. "Got" pigs are some piglets that will be slaughtered aged 3 months at the latest (20-30 kg) or sold to become "thit" (Figure 11). Some farmers are specialized in rearing "got" pigs (n=4) that they sell for slaughter or on to "thit" pig farmers (n=3). However, the weight of animals at sale remains greatly conditioned by the market price and the number of available places in sheds. In this way, each farmer chooses what he considers is the right moment to sell. Both how much any one farm produces and the number of animals kept at any one time are therefore difficult to calculate exactly.

The feed given to animals varies from traditional feed produced on the farm to balanced feed and concentrates offered by the big manufacturers, i.e. Vina Feed, Cargill, Japfa ComFeed, Guyomarc'h, CP, Proconco. Feed rations are made up of rice and maize husks, and industrial feed. They are topped up with floating vegetation such as water hyacinths and spinach, banana tree stalks, potato and sweet potato leaves and kitchen waste. Feed is given in the form of a cooked soup. These mixed diets make it impossible to predict the digestibility and the quantities of rejected excreta, except for animals of exotic races that are only fed with industrial feed (n=6).

Market orientations of pig production

Pork is above all considered as a product for sale. Home consumption and sale from the farm not being very developed, 80 to 90% of fattened pigs are sold. Indeed, country-dwellers do not consume much pork compared with urban Vietnamese. Surveys in rural areas have shown that between 40 and 64% of people questioned ate pork meat less than three times a month. On the other hand, in Haiphong, consumption is apparently daily for 40% of families and every other day for 46% [START_REF] Goulven | Commercialisation d'un produit agricole dans un contexte économique de transition: la filière viande porcine de Nam Thanh à Hai Phong[END_REF].

There are three commodity chains for marketing pork (10): Short circuits supplying the local market, within the district, and involving only one kind of stakeholders lower down the chain, local slaughterers/retailers; a short commodity chain supplying Thai Binh from the districts in-volving two actors, local slaughterers and urban retailers; and a long commodity chain supplying Hanoi and the port of Haiphong, the closest export centre, involving several actors lower down the chain: collectors, slaughterers, urban wholesalers, retailers and exporters. This commodity chain is the best organized one, with contracts that bind farmers to collection companies.

Although a few big commercial farms currently rear more than 200 pigs a year, nearly all production is fragmented and carried out by myriad small-scale family farms. 10% of farmers are farrowers. 80% are fattening-to-finishing pig farmers of which 60% are carrying out a low-earning supplementary activity with less than 6 pigs a year. Then come those who produce more than 6 pigs a year with high feed costs (less than 10%) and those who manage to reduce these costs and maintain a profitable activity (15 to 25%). In addition, some farmers pre-fatten pigs ("Lon got") which provides a good source of income [START_REF] Coq | Ecopol, an integrative and participatory approach for concerted design of public decision. séminaire PAOPA "des approches inovantes au service du développement agricole[END_REF]. Producers are not very specialized. Even on family farms and farms, it is rare to find a pork producing operation on its own. The system of land distribution, applied more strictly in Thai Binh province than in the provinces in the south of the country, allocates an area of land to each family for crops determined by the number of members in a household. The livestock farmer is therefore always a crop farmer. Inhabitants also often possess a fishfarming pond. Just like pig farming, fish farming is practised in a more or less intensive fashion depending on the goals of the farmer. The leader of a commune questioned explained: "we all have pigs, chickens, paddy fields and fruit trees and many also have fish-farming ponds. You could say therefore that we are all partly livestock farmers, arable farmers and fish farmers, all at the same time."

The livestock farmer can thus choose to develop his pig husbandry while also developing or maintaining other activities, such as ducks, fish, gardens, tea, etc., but often the pig farming operation is enlarged to the detriment of other farming activities, orchard or pond. This kind of pig farmer is very opportunist. The number of pigs reared can be multiplied in a very short space of time if the prices of meat are favourable. Similarly, the pig farming operation can decline very rapidly and be replaced by other more profitable activities such as chicken or duck farming. These farmers usually seek to expand their pig farming activities when the context is favourable. But they are often limited by available space. For example, prices go up before Têt (lunar New Year, between the end of January and the beginning of February). The winter months are a prosperous period and farmers fill their buildings to maximum capacity. Conversely, the market slumps in the summer months. Some sheds are on occasion emptied and used for other farming activities (storage of rice, chicken coop).

In a second kind of family farm, pig farmers seek to construct another building because the one near their dwelling is no longer big enough. So they put up a building on an available plot of land. The farmers then have a choice between constructing only a pig production unit or setting up an integrated system. The consequences of the avian influenza epidemic in 2004 and 2005 on the total numbers of birds have not been calculated, however poultry farming, even reduced, is still very prevalent.

Other animal husbandry

ii) Ruminants -There is not much cattle and water buffalo farming, mainly because land available for foraging is scarce in the area, and because of the low demand for cattle and dairy produce. Most of these animals are used for work, the females calving once a year and the calves being sold very young.

Box 2: The concept of a "farm" in Vietnam

A "farm" or "big" farm is an industrial farming operation typified by the desire of the owner to specialize in one kind of production. System specialization often involves the enlargement and intensification of the farm. The "farm" is thus differentiated from other farms by: its size or the size of its herd, the large-scale investments of the owner, and the technical know-how of the farm manager.

Official definitions of the various farm structures producing pigs:

-A farm is an operation involving more than 20 sows or more than 100 pigs. -Family farms house between 5 and 19 sows, or between 19 and 99 pigs. -Small producers possess less than 5 sows or less than 19 pigs.

iii) Fish farming -There are various kinds of fish farming, but the most widespread is extensive mixed farming of herbivorous carp. Produce is mainly consumed by the household, due to the small surface area available per family. Yields are low, about 2 metric t/ha. Many households have dug a pond in their garden with the joint aim of having an expanse of water and of extracting earth for making building bricks. These ponds are used for subsistence fish farming and for growing floating vegetation to add to pig feed. However, over the last few years, fish farming has emerged as less of a secondary activity, but as a profitable form of livestock farming in its own right.

Farming activities are stocking with young fish and fattening. Four species of fish are reared in the same ponds: the common carp (Cyprinus carpio), the herbivorous carp (Ctenopharyngodon idella), the silver carp (Hypophthalmichthys molitrix) and the bigheaded carp (Aristichthys nobilis). It is possible to start fishing about 2 months after releasing the young fish, even if the fish are naturally bigger if they are caught later. Many fish are caught when the pond is emptied in December, before Têt. Feed varies depending on how intensive the system is: animal (and human) excreta, grass and leaves (maize, floating vegetation, etc.) and with increasing frequency, industrial feed. Soups made with broken rice and rice husks are also prepared. On less intensive fish farms, the farmer washes dishes and buckets used to prepare pig feed in the pond.

Box 3: The VAC system

VAC is an acronym for "Vuon -Ao -Chuong" in Vietnamese, meaning "Garden -Pond -Livestock shed". This is a system that works by integrating different kinds of farming physically close to each other. It enables the recycling of nutrients and water between the various kinds of production. It also enables a diversification of produce that makes it possible to limit the risks of price fluctuations. Livestock farming supplies the family with a source of protein, fertilizer and the basis of fish feed (thanks to the organic matter). The pond produces floating vegetation, the basis of animal feed, and also makes it possible to rear fish, diversifying the family's diet. Finally, the rice crop is the staple element of the human and animal diet. In the garden, fruit trees, vegetables or other crops help diversify and balance diet. The organic fertilizing matter produced is absorbed by these various crops. Traditional to Vietnam, this system obtains an optimum yield from surface areas that are often limited. Initially, the pond was dug to supply building material for the house and to create the garden. The garden had a particular importance, as it was the only place where families were free to plant the trees or crops of their choice rather than those they were obliged to plant. The system has become widespread and today most farms, small and medium-sized, operate in this way. Waste from livestock (pigs, poultry, cattle and water buffalo) and from dwellings (human excrement) occupies a key role in the integration of the different kinds of farming within the traditional VAC system [START_REF] Dao The | Changements récents de l'agriculture et défis du développement rural au Vietnam[END_REF].

Changes in integrated production systems

While animal and vegetable produce have been presented separately for practical reasons, the reality is otherwise: the Delta's traditional production systems are integrated. Duck farming, needing an expanse of water, is usually combined with fish farming. The VAC system is very widespread in the province (Box 3). Livestock effluents are the source of nutrients for plants grown, gardens, fish and the aquatic microflora in ponds and therefore play an important role.

As for with pigs, more intensive units are established near or outside dwelling enclosures. Fish farming is on the increase; the local authorities and the technical agricultural services support the conversion of lowyield paddy fields into fish-farming ponds (Box 5), according to the logic of maximizing the added value per hectare and of agricultural diversification. The State encourages the development of fish farming, in particular in Thai Binh province. A project has been established for the period 1999-2010 that aims to increase the volume of exports of farmed fish produce at the national level. Vietnam hopes to reach 2 million metric tons of farmed fish produce exported by 2010, or 2.1 billion Euros. The different aims of the project are to improve the current state of more than 6,000 ponds and to convert low-yield paddy fields into freshwater ponds according to the rice -fish system. The State, through the communes and the districts, subsidizes work up to 7,000,000 VND (equivalent to 369 Euros) per hectare of paddy fields converted into ponds. Between 2001 and 2004, the area of paddy fields converted into ponds totalled 1,907 ha, of which 40% ponds and 60% rice-fish farming. In all the communes visited during surveys, Thai Binh province encourages the consolidation of livestock farms and fish-farming ponds in specialized areas far from dwellings.

Box 4: The policy of "specialized areas": a tool for the development of pig farming

The specialized areas are demarcated areas in each commune where entrepreneurs are encouraged to invest and farmers to consolidate their land, to convert it and to specialize. The final aim is to favour intensification, pig and fish farming. These areas, bringing several farms together, aim to improve livestock farming efficiency and to facilitate access to veterinary care and deliveries of animal feed. They are also designed to ease problems of transport, drainage, effluent management and marketing. Officially, these special areas must respect several criteria: -Their creation and development take into account the areas' potential and local conditions. However, the priority is to create them on land with a low rice yield, far from dwellings, or on land near the Red River (to ease the building of infrastructure). They must also be accessible and served by infrastructure; -They must be models of technical development, with an efficient improvement in the management of industrial livestock farming (reproduction, feeding, processing). The quality of produce must be a priority. Veterinary services must be strengthened and health safety guaranteed; -The development of livestock farming must be linked to that of crop farming, to industrial processing of produce and to animal feed. In this way, these areas must encourage industrial feed and agricultural produce processing companies to open factories in the area, and must set aside land for growing animal feed crops (maize, soya); -Finally, they must be models of respect for the environment: accessible, far from dwellings, containing enough water sources for livestock farming and for treatment of effluents.

Figure 1 :

 1 Figure 1: location of Thai Binh province (Atlas Vietnam, 2001)

Figure 3 :Figure 4 :

 34 Figure 3: Ombrothermic diagram for the year 2004 (Thai Binh Climate Station)

Figure 5 :

 5 Figure 5: Provincial soil map

Figure 6 :

 6 Figure 6: Map of land-use in the province

Figure 9 :

 9 Figure 9: Development of the pig herd 1993-2004 (1)

Figure 10 :

 10 Figure 10: Distribution maps of total pig production, pig herds, pig herds>10 sows

  In this sample, 70 % of farmers possessed at least one sow. The rearing of exotic breeds of sows is limited to large-scale units equipped with installations suitable for intensive farming, such as individual stalls, maternity sections and open metal flooring. Most farmers prefer to keep local Mon Cai sows that are less demanding technically and financially. Exotic breeds of sows are found only on farms with over 5 animals (Table12). Farrowers are often fatteners. Only two farmers are exclusively farrowers. 30 % of pig farmers questioned were exclusively fatteners (n=12). Pigs fattened for meat are type F1 (Mon Cai x exotic breed) or F2 (F1 x exotic breed). Pure breed Mon Cai pigs are only bred together to produce fresh sows.

Figure 11 :

 11 Figure 11: Fattening strategies observed on the farms

Figure 12 :

 12 Figure 12: Pig-Fish Farming Association Thai Binh, 2005

Table 1 :

 1 Evolution of the consumption of meat during the last decade in Vietnam (kg/inhab/year) V. Porphyre, Nguyen Que Coi (Editors), 2006. Pig Production Development, Animal Waste Management and Environmental Protection: a Case Study in Thai Binh Province, Northern Vietnam. PRISE publications, France.

	Year	1991	1992	1993	1994	1995	1996	1997	1998	1999	2000
	Total	14,5	15,5	16,6	17,7	18,3	19,3	20,2	21,1	22,3	23,3
	Pork	10,7	11,6	12,6	13,5	14,0	14,8	15,5	16,3	17,2	18,0
	meat

Table 2 :

 2 Selected socio-economic indicators related to the Vietnamese

agricultural sector Figure 2: Map of population distribution in Thái Bình province

	General context of a dynamic agricultural sector
	in the Red River Delta
	Item	Year	Value
	Land area per capita (ha)	2000	0.41
	GDP growth (%)	2000	6.75
	Agricultural growth (%)	2000	1.6
	(Includes agriculture, forestry and fisheries)
	Contribution to GDP of agriculture (%) (Includes agriculture,	2000	24.3
	forestry and fisheries)
	Contribution to GDP of households (%)	2000	32.1
	Fertilizer imports (millions of metric tons)	2001	3.24
	Vegetable exports (millions of USD)	2001	305
	Source: Statistical year book of Vietnam 2001, 2002

A natural environment full of contrasts a) The climate

		December, is the dry season, with abundant sunshine
		and light precipitation; Sunshine is distributed as
		shown in Figure 4 with 1,600 to 1,800 hours of sun-
	The Red River Delta has a humid, subtropical climate,	shine per year (1).
	strongly affected by the East Asian monsoons. In Thai
	Binh province, average annual rainfall is nearly
	1,400mm and the average temperature is 24°C.
	Average humidity is from 85 to 90%. There are three
	distinct seasons, distin-guished by temperature,
	humidity and sunshine:
	Spring, from January to May, is very humid owing to
	almost permanent fog, with light precipitation and low
	temperatures. Summer, from June to September, is
	typified by high temperatures and heavy precipitation
	(Figure 3): 4/5 of annual precipitation takes place
	during this season (4). Winter, from October to

Table 3 :

 3 Population, agricultural land area and inhabitant density of Vietnam V. Porphyre, Nguyen Que Coi (Editors), 2006. Pig Production Development, Animal Waste Management and Environmental Protection: a Case Study in Thai Binh Province, Northern Vietnam. PRISE publications, France.

	Year	Population (million inhabitants)	Land (m ha)	Density (capita per ha)
		Total	Agriculture	%	Agriculture	Arable	Agriculture	Arable
	1990	66.0	47.1	71.4	6.7	5.3	9.8	12.5
	1991	67.2	47.8	71.1	6.8	6.4	9.9	10.5
	1992	68.4	48.6	71.1	7.0	5.5	9.8	12.4
	1993	69.6	49.3	70.8	7.1	5.5	9.8	12.6
	1994	70.8	49.9	70.5	7.1	5.5	10.0	12.9
	1995	72.0	50.5	70.1	7.1	5.5	10.1	13.1
	1996	73.2	51.0	69.7	7.7	5.6	9.5	13.1
	1997	74.3	51.5	69.3	7.8	5.7	9.5	13.0
	1998	75.5	51.9	68.7	8.1	5.7	9.3	13.2
	1999	76.6	52.2	68.1	8.7	5.8	8.8	13.2
	2000	77.3	52.6	68.0	9.3	5.8	8.3	13.3
	2001	78.7	53.0	67.3	9.4	6.5	8.4	12.1
	2002	79.7	53.6	67.3	9.4	6.6	8.5	12.1

Table 4 :

 4 Chemical characteristics of the alluvial soils located within Red River dikes; soil not renewed by the River's annual flooding

	Village	Depth	OM	pH	Total elements	Available	Exchange
	(District)	(cm)	%	H2O		(%)		elements	cations
								(mg/1000g soil)	(meq/100g soil)
					N	P2O5	K2O	P2O5	K2O	Ca ++	Mg ++
	Vu Dong	0-15	3.38	4.90	0.17	0.07	2.12	2.48	10.00	5.37	1.37
	(Kien Xuong)
		15-25	2.75	4.80	0.16	0.05	2.20	2.77	10.00	6.50	4.62
	Hoang Dieu	0-15	2.13	4.60	0.18	0.06	1.67	5.12	11.00	6.10	3.50
	(Dong Hung)
		15-25	1.15	5.10	0.09	0.03	2.23	2.47	7.00	6.00	6.70
	Quynh My	0-15	2.08	5.95	0.19	0.07	1.55	19.22	7.00	7.50	2.87
	(Quynh Phu)
		15-28	1.45	7.36	0.12	0.07	1.24	20.64	4.00	7.50	2.37

Table 5 :

 5 Chemical characteristics of the alluvial soils located outside Red River dikes; soil renewed by the River's annual floodingGeneral context of a dynamic agricultural sector in the Red River Delta

	Village	Depth	OM	pH	Total elements	Available	Exchange
	(District)	(cm)	%	H2O		(%)		elements	cations
								(mg/1000g soil)	(meq/100g soil)
					N	P2O5	K2O	P2O5	K2O	Ca ++	Mg ++
	Vu Doai	0-15	2.47	6.35	0.23	0.09	1.77	11.44	6.00	9.30	2.50
	(Vu Thu)
		15-25	1.37	6.65	0.13	0.05	1.43	15.44	6.00	10.00	2.00
	Hiep Hoa	0-15	2.52	6.00	0.24	0.05	1.87	13.02	6.00	8.70	3.50
	(Vu Thu)
		15-25	1.37	6.20	0.11	0.02	1.77	19.08	5.00	8.60	3.30
	Quynh Ngoc	0-15	2.08	6.40	0.19	0.07	1.55	19.22	7.00	7.12	2.12
	(Quynh Phu)
		15-28	1.45	6.48	0.12	0.07	1.24	20.64	4.00	6.75	1.62

Table 6 :

 6 V. Porphyre, Nguyen Que Coi (Editors), 2006. Pig Production Development, Animal Waste Management and Environmental Protection: a Case Study in Thai Binh Province, Northern Vietnam. PRISE publications, France. Soil use in Thai Binh, example of Vu Thu district

	Types of soil use	Vu Thu	Thai Binh province
	Ha	%	Ha	%
	Total area	19,843		154,601
	Agricultural area	12,045	61	96,469	62
	-Annual plants	10,697	54	91,424	59
	Rice growing	9,318	47	87,491	57
	-Perennial plants	692	3	1,513	1
	-Gardens	656	3	3,386	2
	Fish farming area	1,173	6	7,309	5
	Forests exploited	0	0	3,394	2
	Public works	3,150	16	26,569	17
	Dwellings	1,655	8	12,443	8
	Area not used	1,820	9	8,494	5
	Source: Thai Binh Statistics Office, 2003
	1 dat thap
	2 dat trung binh
	3 dat cao

Table 7 :

 7 Characteristics of the two primary hydraulic ponders of Thai Binh

	ponder	Area cultivated		Projected area
			Irrigated	Area irrigated/A. culti-	Drained
				vated
	North Thai Binh	58,907 ha	56,109 ha	95.25 %	73,923 ha
	South Thai Binh	44,053 ha	40,970 ha	93.00 %	47,225 ha
	Provincial total	102,960 ha	97,016 ha	94.22 %	121,148 ha
				Source: MARD, 1993

Table 8 :

 8 Capacity of public pumping stations in Thai Binh province

	Number of	Area irrigated		Area drained		Number of	Capacity
	pumping	(ha)		(ha)		pumps
	stations	theory	reality	theory	reality		m 3 /h	kw
	377	50,000	31,000	25,000	20,000	1,044	1,448,060	37,875
						Source: MARD, 1993 (VIE/89/034)

Figure 7: Example of crop rotation in Vu Thu District in 2004 (areas in ha)

[START_REF] Vu | Recommandations en fertilisation organique pour les principales cultures annuelles[END_REF]

Table 9 :

 9 Distribution of irrigated area by type of irrigation in Tien Hai districtSource: Hydraulic Company of Tien Hai district, Thai Binh, 2003 Thai Binh's hydraulic management is very hierarchical and top-down: the Thai Binh Provincial Department of Agriculture and Rural Development (DARD) deals with hydraulic development and management policy in the province; the Provincial Hydraulic Department (PHD) is under the management of the Province's DARD and takes care administratively of all the irrigation works and of drainage at the provincial level; the Provincial Dikes Department (PDD) is under the management of the DARD and takes care of all maintenance work on the dikes and of flood and typhoon response at the provincial level; the 2 Hydraulic Companies of the 2 North and South ponders are under the management of the PHD and each is responsible for providing water to the District Hydraulic Companies in each ponder; the District Hydraulic Company is under the management of the PHD and is responsible for irrigating and draining the communes in its district; the District Office of Agriculture and Rural Development is managed by the District People's Committee, co-ordinates with the PDD, and looks after the dikes; the Agricultural Cooperative takes care of irrigation and drainage on its territory. Due to decollectivization and local history, there are several kinds of agricultural co-operatives in Thai Binh at different levels, namely: i) The communal agricultural co-operative that takes care of irrigation for the whole commune; ii) The inter-village agricultural co-operative that takes care of the irrigation of a few villages in a commune; et iii) The village agricultural cooperative that takes care of the irrigation of a single village. Finally, farmers who water their land must pay a charge for irrigation water and drainage. This tax is collected by the agricultural co-operatives and goes to the hydraulic company. This charge is calculated according to the kind of irrigation/drainage, the crop planted and the growing season.

	Irrigation by public stations		Irrigation by local stations		Gravitational irrigation
							or bailing
	Number of	Area	%	Number	Area	%	Area	%
	stations	irrigated		of stations	irrigated		irrigated
	37	6,863 ha	69	53	1,543 ha	15.5	1,543 ha	15.5

  . Porphyre, Nguyen Que Coi (Editors), 2006. Pig Production Development, Animal Waste Management and Environmental Protection: a Case Study in Thai Binh Province, Northern Vietnam. PRISE publications, France.

Table 10 :

 10 Crop rotations observed among the farmers surveyed

	Month	Feb Ma Apr Ma Jun Jul	Au Sep Oct	No Dec Jan
		Mid-or
		high-level
	Diked-off	land
	land,
	irrigated
		Low-lying
		land

Table 11 :

 11 Evolution of crops production (Mt) for 2002 Animal Waste Management and Environmental Protection: a Case Study in Thai Binh Province, Northern Vietnam. PRISE publications, France.

	Production 2002 (Mt)	Vietnam	France	European Union	World
	Sugar canne	16 823 500		114 000	1 288 403 240
	Cereals	25 035 054	69 123 110	214 158 088	1 837 484 690
	Soya beans	201 400	207 000	791 505	179 917 302
	Maize	2 314 700	16 013 000	40 624 313	602 589 189
	Cassava	4 157 700	-	-	184 852 540
	Sweet potatoes	1 725 100	-	65 635	136 130 396
	Paddy rice	34 063 500	105 000	2 603 700	576 280 153
					Source : FAO, 2003

Table 12 :

 12 Evolution of pork meat production (Mt) from 1990 to 2002 in Vietnam compared to Asia, Europe and USA

	Production 2002 (Mt)	Year
		1990	1995	2000	2002
	World	69 862 273	78 635 452	89 533 448	94 185 700
	Asia		39 826 719	48 385 305	52 430 782
	Europe		24 698 308	25 334 959	24 986 877
	France	1 726 800	2 144 000	2 312 000	2 350 000
	Vietnam	728 560	1 007 000	1 409 015	1 653 595
	United States of America	6 964 000	8 097 000	8 597 000	8 937 000
					Source : FAO, 2003

Table 12 :

 12 Kinds of pig farms, terminology and change over time

	Kind	Local name	Criteria	1993	2004
	Traditional farms	N´ng HÈ	Less than 5 sows (or 19 pigs)	420,000	412,000
	Family farms	Gia Trπi	From 5 to 19 sows (or 19 to 99 pigs)	89	2,452
	Farms	Trang Trπi	More than 20 sows (or 100 pigs)	88	1,335

Table 11 :

 11 Distribution of sows in the farms surveyed Animal Waste Management and Environmental Protection: a Case Study in Thai Binh Province, Northern Vietnam. PRISE publications, France.

				Sow breeds	Number of pig farms
	Number of sows	Number	Average	L	E or C	100%L	L & E	100%E
	(NS)	of farms	NS/farm
	0	13	0
	0<NS<5	18	1,8	100%	0%	18	0	0
	5<=NS<10	6	5,5	85%	15%	4	2	0
	10<=NS<15	3	11	6%	94%	0	1	2
	15<=NS<20	1	17	18%	82%	0	1	0
	NS=20	1	20	0%	100%	0	0	1
	NS=60	1	60	0%	100%	0	0	1
	L: Local breed sows	E: Exotic breed sows C: Exotic*local crossed sows

Minutes of meeting N012-NQ-TU, Thai Binh Provincial People's Committee, August 2004

Acknowledgements

The authors would like to thank Mr. Bui Kim Dong, researcher in water management at DSA/VASI, for his valuable information on water management in Thai Binh province.

Box 5: Land quality and the problem of low-lying land

Diked-off land officially falls into one of three categories: high-level, mid-level or low-lying, which correspond to three different topographical levels. In general, Vietnamese farmers are allocated a little of each of these kinds of land, which have varying values. These differences in altitude can cause differences in access to water and in kinds of crops grown. Thus it is possible on high-level land, in addition to the two classic cycles of spring and summer rice, to grow a third cycle of dry crops in winter. Mid-level land is that on which it is possible to choose the crops to be planted in spring and in summer, as it is not flooded during this period. On the other hand, in winter it cannot receive dry crops as it is subject to flooding. Low-lying land is constantly subject to flooding and is suitable only for growing rice. The Vietnamese government is currently urging farmers in Thai Binh province to convert their low-lying land with low rice yields into fish-farming ponds, in order to increase income per unit of area on this kind of land. The aim of this policy is to reduce poverty.


Alexis Duque
email: alexis.duque@insa-lyon.fr

Razvan Stanica

Hervé Rivano

Claire Goursaud

Adrien Desportes

Herve Rivano

Poster: Insights into RGB-LED to Smartphone Communication

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

In the past decade, the interest in visible light communication (VLC) has rapidly grown in the research community, opening the door to novel usages and commercial applications. A particularly interesting field of VLC is the Optical Camera Communication (OCC) that provides a ubiquitous communication link between any light emitting diode (LED) and users through their smartphone camera.

With the fast smartphone market expansion, LED-tosmartphone communication opens the door to many commercial applications e.g. indoor localization, contextual information broadcast or interaction with IoT devices like smart toys. Consequently, since the seminal work by Danakis et al. [START_REF] Danakis | Using a CMOS camera sensor for visible light communication[END_REF], researchers have proposed numerous solutions to bring LED-to-Camera communication to the industry. Nevertheless, most of them study white ceiling LEDs or small monochrome LEDs [START_REF] Duque | Unleashing the power of LED-to-camera communications for IoT devices[END_REF], but RGB LEDs have been forsaken.

As a continuation of our IoT device to smartphone communication system [START_REF] Duque | Unleashing the power of LED-to-camera communications for IoT devices[END_REF], we propose to increase the channel capacity by replacing the low power 5mm monochrome LED with the equivalent RGB LED. In fact, RGB LEDs are often preferred to monochrome LEDs in commercial electronics since their color can be changed at runtime. We applied the methods found in the literature for power ceiling RGB LED to smartphone communication [START_REF] Chen | Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera[END_REF][START_REF] Hu | ColorBars[END_REF][START_REF] Ryu | RGB MIMO Optical Camera Communication with Histogram Equalization[END_REF] and we faced unexpected behaviors due to the weak power and the difference in the LED size, making these standard solutions unusable in our system at this point.

After some investigations, we share in this paper our first findings, discuss the remaining challenges and propose candidate solutions we expect to ease the decoding process.

RGB LED as emitter

An RGB LED is composed in fact of three LEDs: red, green, and blue, inside one package. Typically an RGB LED has four pins: one common pin that is connected to ground and one for each of the three LEDs. This allows a program to vary both the color and the color intensity level of the RGB LED.

Modulation Schemes: while On-Off keying (OOK) combined with the Manchester line code is usual for monochrome LEDs [START_REF] Danakis | Using a CMOS camera sensor for visible light communication[END_REF][START_REF] Duque | Unleashing the power of LED-to-camera communications for IoT devices[END_REF], Wavelength Division Multiplexing (WDM) and Color-Shift-Keying (CSK) have been proposed for RGB LEDs respectively by Liang et al. [START_REF] Liang | RGB visible light communication using mobile-phone camera and multi-input multi-output[END_REF] and by Chen et al. [START_REF] Chen | Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera[END_REF]. WDM schemes modulate the three color channels1 independently with distinct input data. On the contrary, in the CSK scheme, the transmitted bits match specific color coordinates in the color space.

Achievable Color and Frequency: we experimentally found the color we can obtain with our low-cost hardware to establish a suitable modulation scheme and we defined a constellation of symbols. the green channel state is not easily determinable for the symbols for which the green is mixed with another color.

Identifying Challenges

2) Color diversity across devices, camera settings and ambient light: various smartphones will render the colors differently and that behavior also happens on the same device when the ambient lighting conditions change or by modifying the ISO, exposure and white balance settings. Fig 1 shows the color rendered when changing the ISO setting of the camera.

3) Intra-frame color diversity: this phenomenon is shown in Fig. 2, where the symbols are completely disparate across the regions considered in the picture.

4) Color mixing issue with the cheap low-power RGB LEDs: as shown in Fig. 3, even without modulation and with proper use of the RGB LED, the colors are not perfectly mixed so that two or three color beams are visible. However, to exploit the rolling shutter effect, we expect that the color remains the same along a row of pixels when the LED is not modulated.

5) Real-time implementation: color detection requires complex computer vision algorithms that need a threedimensional matrix as input. That is three times larger than the one for a monochrome LED. Previous works [START_REF] Hu | ColorBars[END_REF][START_REF] Chen | Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera[END_REF][START_REF] Ryu | RGB MIMO Optical Camera Communication with Histogram Equalization[END_REF] all present a compute-intensive demodulation method using Matlab or OpenCV on a computer. A real-time algorithm implementation on a smartphone has not been unveiled yet.

Solutions Proposal

We are proposing and currently testing a few methods to overcome the issues we have presented in Sec. 3.

Demodulation methods: a demodulation method within the LAB color space would be preferred, as only two vectors Figure 4. On the bottom, the red channel input with the regular f csk CSK modulation. Above, the CSK modulation is combined with a f pwm PWM and f pwm /2 PWM so that dark and light stripes will appear within the CSK symbol period. (A and B) describe the chromaticity, instead of all the three for the RGB color space. Because the computer vision algorithms are particularly adapted to the GPU architecture, using the smartphone GPU can considerably fasten the demodulation process compared to a CPU implementation. This can be done using Renderscript framework on Android, and the Apple Metal 2 framework on iOS.

Use the Pulse Width Modulation (PWM): by modulating a PWM output, configured with a frequency f pwm , higher than the CSK frequency f csk , but below the CMOS sensor sampling frequency, we can induce stripes more or less spaced within a CSK symbol. That method may extend the range of symbols as it is shown in Fig. 4.

Constellation choice: we propose to use a combination of M-CSK and N-PWM modulation schemes. Samples of symbols are shown in Fig 5 . Based on the observations in Sec. 2, we found that the N PWM frequencies f i pwm must be 16 ≤ f i pwm ≤ 22 kHz to comply with the camera shutter bandwidth. To avoid inter-symbol interference (ISI), i.e. to be able to determine the difference on the stripes spacing, two adjacent PWM frequencies f i pwm and f i+1 pwm must be spaced with ∆ f ≥ 2kHz.

Thus, each channel has 6 states, e.g. for the green channel:

G f 1 pwm , G f 2 pwm , G f 3 pwm , G f 4 pwm , G ON , G OFF with f i pwm = {16
, 18, 20, 22} kHz, i = 1, . . . , 4. However, we make the hypothesis that choosing symbols where f pwm varies in many channels will cause unmanageable ISI.

Furthermore, using the PWM modulation on only the green channel will help the color identification process so that the green channel state can be inferred from the presence of stripes.

Conclusion

In this work, we point out through a series of experiments the challenges of RGB LED to camera communication. We proposed several ideas that we expect to ease the decoding process. These algorithms and methods are under development and implementation. In a future work, we will conduct and extensive experimentation campaign to evaluate and (in)validate the hypothesis presented in this work.

6 References

Figure 1 .

 1 Figure 1. The same symbols observed with different ISO and white balance camera settings.1) Limited number of symbols that the RGB LED can produce: the RGB LED can produce only a few colors. Some of these symbols seem to be very close and so, are often difficult to distinguish. The experiments bring out that

Figure 2 .

 2 Figure 2. The same 8-CSK symbols sent consecutively and repetitively are perceived differently in the picture.

Figure 3 .

 3 Figure 3. The RGB LED without modulation. On the left, the LED is strongly dimmed with the 3 channels ON. On the right, the LED is normally dimmed with only the red and green channel ON.

Figure 5 .

 5 Figure 5. The 8-CSK modulation symbols combined with a 20 kHz PWM on the green channel only.

In this paper, color and channel are synonyms.