MPEG-4 Video Transmission using Distributed TDMA ...

MPEG-4 Video Transmission using Distributed TDMA MAC Protocol over IEEE 802.15.4 Wireless Technology Nor-Syahidatul N.Ismail, Farizah Yunus, Sharifah H.S.Ariffin, A.A Shahidan, Rozeha A.Rashid, W.M.A.E.W.Embong, Norshiela Fisal, S.K.S.Yusof UTM-MIMOS Center of Excellent Faculty of Electrical Engineering Universiti Teknologi Malaysia UTM SKUDAI 81310 Johor MALAYSIA [email protected] Abstract

The issues of green technology nowadays give an inspiration to the researcher to make all the future design to be energy efficient. Medium Access Control (MAC) layer is the most effective layer to provide energy efficient due to its ability to control the physical radio directly. One of the important applications in the future is a video transmission that can be transmitted with low-cost and low power consumption. MPEG-4 is one of the international standards for moving video. MPEG-4 provide better compression and primarily design at low bit rate communication. In order to achieve good quality for video application, the design at MAC layer must be strong. Therefore, to increase the performance of the MPEG-4 in IEEE 802.15.4, in this paper we propose a cross layer design between MAC layer and Application layer. A priority queue will be implemented at MAC scheduling depends on the level of frame important in MPEG-4 format frame. A distributed Time division Multiple Access (TDMA) will be used for MAC protocol to provide reliable data transmission for high priority frame.

1. Introduction

Wireless communication plays an importance role in telecommunication sector and leads the development of Wireless Sensor network (WSN) technology. WSN has received considerable attention over a past few years due to their wide range of potential application such as environmental monitoring, target detection and surveillance application [1]. The video transmission over WSN promising good solution for green technology in the future development, In WSN, IEEE 802.15.4 is a new standard for low rate wireless personal area network (LP-WPAN). MPEG-4 is a video codec standardized by the Moving Picture Expert Group (MPEG) for low bit rate digital media applications. It already proven that the MPEG-4 video can transmit via IEEE 802.15.4 network [2]. The possibility of transmit MPEG-4 (compressed video) in LR-WPAN would allow us to transmit image in low cost communication networks with wireless connectivity [2].

One of the most critical issues in order to prolong network lifetime in WSN is the energy efficient. MAC protocol is the most effective layer to provide energy efficient due to its ability to control the physical radio directly [3]. In wireless sensor network, energy wastes in transmission medium are collision, overhearing, idle listening and overmitting[1][4]. Thus, this problem can be overcome with proper MAC layer design consideration based on energy usage. In this paper, we proposed cross layer design between Application layer and MAC layer. This approach will allow the scheduler to transmit the frame depends on its priority level in priority queue in MAC layer. To achieve energy efficient, TDMA MAC protocol will be used in this project. The rest of paper is organized as follows. Section 2 discuss on the related works on distributed TDMA MAC protocol and MPEG-4 transmission over wireless technology. Our proposed cross layer architecture lies in section 3. Section 4 elaborates the existing protocol analysis. Lastly, section 5 presents the conclusion and recommendation for future works.

2. Related Works

2.1 A Distributed TDMA MAC Protocol TDMA protocol can be group into two categories which is centralized and distributed. In centralized approach, a central node is responsible for deciding who can access the channel, and the duration for which that node has control over the channel. Each sensor node will depends on the central node manager to allocate the time slot for nodes within the cluster. This approach has the disadvantages such as lack of scalability, fault tolerance and high latency. These problems can be solved using distributed TDMA MAC protocol. In distributed TDMA approach, each sensor node allows to assign itself a time slot by collecting its neighborhood information. There has been several number of distributed TDMA MAC protocols developed for WSNs over the past few years such as in [5][6][7][8]. EMACs [5] protocol conserves energy through different node functionality. It has three modes of

operation in EMACs protocol which is active, passive and dominant mode. It conserved energy by keeping track of one active node. The active node will forward the data and inform them of network message. But the limitation of this protocol is the passive node has to depend on the active node to transmit the information because only active node controls timeslot. There are three session in EMACs timeslot which are communication request (CR), traffic control (TC) and data. LMAC [6] conserve energy by switches its transceiver to standby state when node is not needed for transmission without different mode of node as EMACs Protocol. LMAC improve EMACs by eliminate one session in time slot. There are only have two session in LMAC timeslot which is control message (CM) and data message (DM). In LMAC protocol, when a node has data to transmit, it waits until its time slot comes up and transmits the packet without collision or interference to other transmission [13]. To assign timeslot in LMAC protocol, there are four operation stages; initialization stage, wait stage, discovers stage and active stage. The limitation of this protocol is LMAC only permit node to own a single timeslot perframe. AI-MAC [7] is a novel distributed TDMA based MAC protocol that adapts an adaptive and informationaware version of the LMAC protocol. The application focus on environmental monitoring that takes certain parameter of the physical environment such as temperature, solar radiation, air pressure and rainfall. Because of that, this protocol proposes data management framework that introduces a multiple Data distributed table (DDT) depending on the parameter of the physical environment. DDTs build into the framework that help make deductions about the kind of data traffic that can be expected depending on the query injected into the network and the distribution of the data that is being generated. The different between LMAC protocol and AIMAC protocol is that in LMAC protocol, every node only allows one time slot within the network. Unlike AI-MAC, it allows to own multiple slots and vary the number of slots depending on the amount of data. This ensures fairness in the sense that the bandwidth allocated to a node corresponds to the traffic it is expected to encounter. But AI-MAC do not consider energy efficient. eL-MAC [8] enhanced protocol developed based on LMAC by introducing Active/Sleep Mechanism for efficient energy usage with predefined duty cycle and leveled Timeslot Synchronization for synchronization process. el-MAC also introducing Adaptive MultiTimeslot Allocation (ATMA) mechanism to allows node to control multiple timeslot. There are three operation stages to obtain timeslot in eL-MAC compare to LMAC that have four stages. eL-MAC protocol increases energy efficiency by combining waiting stage and discovery stage to decrease the time for node to turn into active state. But in eL-MAC protocol, channel is not utilized because once node gets timeslot, it not

release to other node and the implementation of eLMAC only limited to 9 nodes. 2.2 MPEG-4 in Priority Transmissions There are three types of MPEG-4 encoded frames which are I, P and B frame. Figure 1 shows the dependency between each type of frames [9].

Fig. 1: MPEG-4 frame type I-frame is a reference point that is used to start the next Group of picture (GOP) and to resynchronize the video during error in transmission. In I-frame there are several P and B frames that are derived from it. If Iframes are lost during the transmission or corrupted, all the P and B-frame up to the next I-frame are useless. The P-frames are the compressed version of I-frame and have predicted information. The B frame comprised mostly of predicted information from neighboring I and P frame. I-frame has high priority compare to the P and B frame, While P frame has high priority than the B frame. Figure 2 shows the I, P and B frame which are in decreasing order of importance.

Fig. 2: Frame in decreasing order of important There are several researches taking place on transmitting multimedia video via wireless channel such as in [10][11][12]. In [10], Yang Xiao at al., proposed a prioritized frame cross layer transmission scheme between the medium access control (MAC) layer and the application layer over IEEE 802.11e. The video transmission based on priority frame and if I frame lost, all the P and B frame will be discarded. This protocol does not retransmit the I frame and will cause many B and P frame will drop if I frame loss. The MAC layer will become complex if the maximum delay is not handle correctly. This is due to the delay between frames that trigger the dropping of frames and turn the dependence function to drop more frames. In [11], Pilgyu Shin at al., proposed cross layer architecture for video transmission that consists of application, transport and MAC layers. To improve the quality of service (QoS), they used the discriminating MAC method of IEEE802.11e EDCA model according to the level of important frame in MPEG-4. Frame will be prioritized at application layer and transport layer will pass feedback data about network stage to the frame dropping module at the application layer. If the estimated available bandwidth is smaller than the current data transmission rate, the frame dropping module will drops B frame. Adaptive transmission rate control introduces to reduce transmission queue overflow that cause by EDCA method. But the inaccurate bandwidth estimation will cause the module

dropping unnecessary frame and lead to higher packet loss and will decrease the throughput. In [12], the author introduce the priority based ARQ (P-ARQ) for retransmission of packet lost. The retransmission will depend on the stream class (class 1: header, class 2: I frame, class 3: P frame and class 4: B frame). I frame has high probability to retransmit if I frame lost and Round Trip Time (RTT) is less that deadline of the packet lost. Cross layer also propose between application layer and MAC layer where they used IEEE 802 model. But this protocol lack of efficient to control the maximum delay because of lack of wireless channel condition.

3. Proposed work

3.1 Cross Layer Design Architecture For MPEG-4 video transmission, all the authors mentioned in section 2.2 suggested cross layer design architecture in their protocol. Cross layer architecture can enhance the performance of video quality by jointly optimizing the performance of single or multiple cross layer. Besides that, they used IEEE802.11e MAC protocol for wireless local area network (WLAN) and it is different with our project. We implement MPEG-4 transmission over IEEE802.15.4. IEEE802.15.4 is design for Low Rate Wireless personal area network (LR-WPAN) and its standard is designed for low cost and low power consumption. Figure 3 shows cross layer design architecture in this project.

• All frame in MPEG-4 will be classified into different level depends on their priority. I frame for level 0, P frame for level 1 and B frame for level 2. With only one queue, high priority data may experience high delay in the normal FIFO (first in first out) [13]. However, in this project, priority queue is proposed for each frame. Figure 4 shows the propose cross layer between application layer and MAC layer. For the routing protocol in the network layer, we take advantages of adaptive routing scheme. In this project we used RTLD (real time with load distribution) routing protocol [14]. In RTLD routing protocol, the parameter from physical layer (SNR, RSSI, battery) will be used to find optimum node in routing decision. Figure 5 shows the interaction between network layer and physical layer in RTLD routing protocol.

Fig. 4: Cross Layer Design between Application Layer and MAC Layer

Fig. 3: Propose Cross Layer Design Architecture To improve video quality in MPEG-4 transmission, we propose cross layer design between medium access control protocols (MAC) and Application layer. There is three typse of frame in MPEG-4 according to level of important as mentioned in section 2.2. In the proposed approach: • All frames are prioritized at the MAC layer, so the I frame have higher priority than the P frame, and P frame have higher priority than B frame. • In the transmission queue of MAC layer, the frames will be scheduling based on priority frame. Different priority queues are proposed in MAC layer. • I frame will be transmitted in two different route to make sure the reliability of the I frame. • If P frame and B frame lost, no retransmission needed.

Fig.5: Cross Layer Design between Network Layer and Physical Layer in RTLD Routing Protocol

3.2 Timeslot Allocation and Frame Structure In Distributed TDMA MAC protocol, every node will assign its own time slot based on neighbor information. Every node will listen to beacon signal to collect the neighbor information for time slot allocation and synchronization process. Figure 6 shows propose MAC frame structure.

This adaptive distributed time slot allocation approach allows each node in the network a chance to transmit data. Timeslot allocation for I frame is highest than others frame. That is because I frame contain highest amount of information and the basic of reconstruction of the video stream. Thus, a single I frame has to be transmitted using much greater number of time slots. 3.3 Energy efficient MAC protocol propose The main challenge in designing protocol in wireless sensor network is to design MAC layer protocol to be energy efficient. Figure 7 shows the sleep/listen mode scheme for energy efficient in MAC protocol proposed. Nodes switch to sleep mode if there is no data to transmit or received. Each of nodes will wake up at the beginning of time slot to listen for beacon message of their neighbor. The beacon message will be used for synchronization process and for exchange neighbor information.

Fig. 6: Propose MAC frame structure In the initialization phase, contention based protocol will be used to select the best neighbor using RTLD routing protocol. After deciding the best candidate to forward data, the nodes randomly selected timeslot to forward the data. The allocation of timeslot will depends on the approach mention in section 3.2. There is several research that combine contention based and TDMA based in their works for channel access [15][16][17]. By using contention based in initialization phase, it makes the protocol more scalable and cognitive. The routing protocol will chose the optimum node to forward the data depends on the current network status. In RTLD routing protocol, the optimal forwarding probability is applied to select the optimal forwarding choice based on maximum velocity of a packet moving through one-hop, packet reception rate (PRR) and remaining power for every one-hop neighbor[14]. On the other hand, time slot approach was used for channel access to avoid collision problem between neighbor nodes. In this project, we will adapt eL-MAC protocol to provide a better performance in terms of packet received ratio and efficiency in energy usage. The features of eLMAC protocol are [8]: i. Distributed time slot allocation. ii. Active/sleep mechanism for efficient energy with predefine duty cycle iii. Leveled timeslot synchronizations iv. Adaptive Multi Timeslot Allocation (AMTA) [18] Some enhancement will be done on distributed timeslot allocation where the time slot will be allocated only for sensor node that has data to transmit and depends on the priority scheduling. The number of timeslot allocation will be divide depends on frame priority as shown in figure 6. (Example of time slot=8 time slot). After one frame transmission, nodes in the network will content again to get timeslot allocation.

Fig. 7: Flowchart Sleep/Listen mode scheme

3.4 Adaptive Multi-timeslot Allocation (AMTA) Adaptive multi-timeslot allocation (AMTA) in [18] promising good solution for channel utilization problem that face by TDMA protocol. The AMTA technique allow node to assign its own multiple timeslot in a frame according to the traffic requirement. The advantages of allowing a node to occupied more than one timeslot it that, the node can transfer data packet faster, reduces the queuing delay and increase channel utilization. AMTA technique will monitor the usage of the current controlled timeslot periodically. If the traffic demands higher data transmission rate, AMTA will increase the number of controlled timeslot but if the traffic required lower data transmission rate, AMTA will reduces the number of controlled timeslot in order to allow other node to use it.

4. Protocols Analysis As mention before, we are taking advantage of eLMAC protocol because it gives better performance in term of energy efficient compare to other protocols. In this paper, we compared the performance of LMAC protocol and eL-MAC protocol in term of power consumed and the efficiency of energy usage. The comparison also will be done for eL-MAC protocol with and without AMTA technique. Nodes in the simulation will be place in 3x3 grid topology as shown in figure 8.

Fig. 9: Average power consumed per node The efficiency the energy usage for LMAC and EL-MAC protocol are shown in figure 10. The increment of packet generation rate cause the energy usage per bit received degrades exponentially. The more data being transmitted, the energy usage will be increase. EL-MAC50 and EL-MAC50_AMTA give better performance compare to LMAC protocol. This happens because LMAC spend more time in listen for beacon signal and its timeslot shortest among other protocol. The simulation result also shows that the assist of AMTA technique in eL-MAC protocol produces significant improvement in term of the efficient of energy usage.

Fig. 8: Network topology Figure 9 shows the simulation result of eL-MAC protocol’s compare to LMAC protocol under homogenous unicast traffic condition in term of power consumed. 50 percent duty cycle was used for eL-MAC protocol in this simulation. The simulation shows that LMAC consumed more power compare to EL-MAC50 and EL-MAC50_AMTA. This is because the sleeping time for LMAC protocol is the shortest among other protocols. EL-MAC50 and EL-MAC50_AMTA consume approximately half of the power usage for LMAC protocol. EL-MAC50_AMTA shows the best performance as the listening time for beacon message where the timeslots in a frame is fully utilized by the contended nodes.

Fig. 10: Average energy used per bit received

5. Conclusions and Recommendation

In this paper, we present our propose work on MPEG-4 video transmission over wireless sensor network. A distributed TDMA approach was used as channel access to avoid collision while transmit frame. The Contention based protocol was used in initialization phase is to make the network more scalable and cognitive. To increase the quality of video transmission, we propose cross layer design between MAC layer and Application layer. In our approach, the parameter in application layer (frame type) will be used in MAC layer to schedule the frame based on priority frame. As future work, the proposed protocol will be implementing and simulate in NS2 platform. The results from the simulation will be compared with existing MPEG-4 video transmission application. To achieve high reliability transmission, network coding in the

network layer well be implement since it can ensure the reliability through packets combination method [19].

Acknowledgement

The Author would like to thank to the Ministry of Science, Technology and Innovation (MOSTI) Malaysia for sponsorship, UTM-MIMOS Center of Excellent for their full support and good advice and for Research Management Center (RMC) Universiti Teknologi Malaysia. Thanks also to all anynomous reviewers for their invaluable comments ant the guest editors who handle the review of this paper.

References

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