Cooperation in Wireless Grids

Transcription

1 Cooperation in Wireless Grids An Energy Efficient MAC Protocol for Cooperative Network with Game Theory Model Master Thesis Puri Novelti Anggraeni Satya Ardhy Wardana Supervisor : Frank Fitzek

2 Introduction Theoretical Review Problem Definition Proposed Scheme Numerical Results and Analysis Conclusion and Further Works

3 Introduction Battery lifetime is a crucial factor of a wireless devices to support its mobility and quality Higher battery lifetime can support higher mobility and higher data rate in a long term

4 Introduction

5 Introduction Cooperation is proven to reduce power consumption [1] Game Theory is suitable to model cooperation in wireless grids Recent work has not consider MAC layer where energy saving technology takes part Goal : Design an energy efficient MAC protocol [1] F. Albiero, Power saving in cooperative networks: A game-theoric approach, Master s thesis, Universita Agli Studi di Padova (Italy) and Aalborg University (Denmark), 2005.

6 Introduction

7 Introduction ASSUMPTIONS All mobile devices have two Network Interface Cards (NICs) IEEE or Wireless Local Area Network (WLAN) is used No hidden / exposed devices problem occurred due to close proximity No significant interference is experienced by other clusters due to channel assignment Power components in the mobile devices are ideal thus no overhead in changing state

8 Introduction Theoretical Review Problem Definition Proposed Scheme Numerical Results and Analysis Conclusion and Further Works

9 Motivation to Cooperate Cooperation is a strategy of a group of entities that work together to achieve a common or individual goal Every entity gains advantage by giving or sharing its resources P c,rx + P s,tx + (n-1) P s,rx < n P c,rx

10 Game Theory Game theory is a mathematical model for the analysis of interactive decision making processes where the decision of a player influences others and overall system A game consists of three basic components: a set of players, a set of actions, and a set of preferences

11 CSMA / CA CSMA/CA is the MAC layer protocol employed in IEEE or WLAN

12 Power Management in IEEE Power Mode in a IEEE devices is consisted of Awake and Doze states The states are consisted of : Transmit Receive Sense Idle

13 NetLogo NetLogo is a programmable modeling environment for modeling complex systems which are developing over time Modelers can give instructions to hundreds or thousands of independent agents concurrently This tool can be well suited for the distributed (e.g ad hoc) and centralized (e.g cellular) network and game theory

14 Introduction Theoretical Review Problem Definition Proposed Scheme Numerical Results and Analysis Conclusion and Further Works

15 Ideal System Ideal System Setup Full TDMA system Not consider MAC layer Theoretic Analysis F. Albiero, Power saving in cooperative networks: A game-theoric approach, Master s thesis, Universita Agli Studi di Padova (Italy) and Aalborg University (Denmark), 2005.

16 Ideal System Cooperative Strategy Question : Optimize Individual Gain or System Gain? Wise MD 3 Selfish MD 1 MD 2

17 Cooperation in Existing System IEEE System Setup TDMA for access point access CSMA / CA for MAC protocol inside a cluster

18 Performance Evaluation Comparison of Ideal and Existing System Performance

19 Introduction Theoretical Review Problem Definition Proposed Scheme Numerical Results and Analysis Conclusion and Further Works

20 Proposed Scheme for an Energy Efficient MAC Layer in Cooperation Motivation CSMA/CA implementation in the cooperation raises the energy consumption Goal Propose a scheme for an energy efficient MAC protocol The benefit of cooperation in terms of energy saving gain is optimized (close to the ideal case) The scheme should be easy to implement reuse the existing protocol with new scheme

21 Cluster Formation (Before the proposed scheme is performed) Every mobile device creates a link to its possible surrounding mobile devices within certain coverage area and calculates the links between them Every mobile device decides with whom it cooperates (wise or selfish strategy) note : This process is not included in the energy consumption calculation

22 The Proposed Scheme Setup Phase Selection of Head Cluster (Step 1-3) The MAC layer protocol : CSMA/CA Protocol adoption is easier and simple Pilot Tone (Step 4) Time slot assignment for every mobile devices to access the channel Avoid collision Steady State Phase (Step 5) TDMA ; broadcast within cluster

23 Cluster Period : T cluster Interface 1 : cellular link Interface 2 : short range link Ct : Setup Phase Pi : Pilot Tone

24 Cluster Period : T cluster The sequence of setup phase, pilot tone, and data exchange phase is repeated every T cluster N packet : Number of packets (CSMA/CA packet size is 8584 bits) R c : Data rate for the cellular link Short range data rate > Cellular data rate Possibility of idle period in T cluster

25 Introduction Theoretical Review Problem Definition Proposed Scheme Numerical Results and Analysis Conclusion and Further Works

26 Default Values of Parameters Minimum short range data rate : 24 Mbits/s Cellular data rate : 6 Mbits/s Number of mobile devices : 20 Strategy : Pure Wise / Pure Selfish T cluster : ms Number of packet : 25 Mobility : 1 m/s (-10 o to 10 o of turn) Result (Energy Consumption) : Averaged over time and mobile device : Normalized with non-coop

27 Performance Evaluation

28 Impact of Varying Number of Mobile Devices Number of mobile devices : 20, 30, 40, 50 Strategy : pure wise More mobile devices increase the energy saving gain The gain is not increasing linearly as the number of mobile devices increases, due to overhead in setup phase or contention phase

29 Impact of Varying Max. Range in a Cluster (i.e Varying Minimum Short Range Data Rate) Max-range 4 : minimum short range data rate 24 MBits/s Max-range 6 : minimum short range data rate 12 MBits/s Max-range 7 : minimum short range data rate 9 MBits/s Larger max range : more probability that a cluster is using lower data rate, thus energy saving gain may reduce Note : the short range data range is lowest data rate from all link of every pair of mobile devices

30 Impact of Varying Cooperative Strategy In pure strategy (wise or selfish) : Wise strategy perform better energy saving gain In mix strategy : Selfish perform perform better energy saving gain Selfish mobile devices exploit wise mobile devices

31 Impact of Varying Cooperative Strategy

32 Impact of Varying Mobility Distribution Mobility Model Simulation Case Number of Low Mobility (0.1 m/s) Number of Medium Mobility (1 m/s) Number of High Mobility (3 m/s) Case 1 15 mobile devices 2 mobile devices 3 mobile devices Case 2 3 mobile devices 2 mobile devices 15 mobile devices Case 3 7 mobile devices 6 mobile devices 7 mobile devices

33 Impact of Varying Mobility Distribution

34 Impact of Varying Mobility Distribution Different mobility distribution does not effect system performance significantly, as the system reaches its stability Due to close environment (good average over space and players) The system undergone a high fluctuation in the beginning of simulation; In a heterogeneous mobility environment, the system performs differently in a short period of time

35 Impact of Varying Mobility Distribution Each mobile device spends almost similar power regardless its mobility and its mobility case High number of iteration in a close environment good average over space and players

36 Impact of Varying Cluster Period (T cluster ) Based on [1], it is assumed that approximately every 2-3 meters distance difference results in changing the short range data rate If the speed of mobile devices is 1 m/s, then in worst case, the data rate between two mobile device might change after approx. 1.5 seconds (3 meters) T cluster can be changed with the maximum value depends on the mobility model [1] P. Romano, The range vs. rate dilemma of wlans January 2004.

37 Impact of Varying Cluster Period (T cluster ) T cluster period is longer energy consumption will decrease In the case : mobile devices are moving fast it might happen that during the T cluster period, the data rate is changing the energy consumption might change Maintain the current cluster or form a new cluster? Additional overhead to inform the changes of data rate

38 GPRS/WLAN Environment GPRS for Base Station Link 5 and 7 dedicated Timeslots (42.25 Kbits/s and Kbits/s ) T cluster is chosen to be 2.03 seconds Receiving power equals to 2.3 Watt and Idle power equals to 0.04 Watt For 50 wise users

39 GPRS/WLAN Performance

40 Introduction Theoretical Review Problem Definition Proposed Scheme Numerical Results and Analysis Conclusion and Further Works

41 Conclusions The comparison of cooperation in ideal system and IEEE WLAN system shows that cooperation using omnipresent technology does not perform as well as it is expected The proposed scheme gives significant improvement from IEEE The proposed scheme is also feasible to be implemented in existing technology

42 Conclusions It is also found that the proposed system works better under higher number of users, higher cluster period, and in pure wise strategy Smaller cluster size, indicates higher short range data rate, also contributes to better system performance and may lead to proposed system performing closely to ideal system

43 Future Works The procedure for members joining and leaving a cluster during cluster period Hardware imperfection can also cause higher energy consumption Changing power state may not be as ideal as it is in this work

44 DEMO

45 Thank You

46 Errata Page x : in the second row, the word "their" should be changed to "his" Page 8 : the corecet equation should be like the following : P c,rx + P s,tx + (n-1) P s,rx < n P c,rx Page 35 : the title of Section 4.1 should be "The Proposed Scheme"