Video on Demand Caching System using NIPBCS over Mobile Ad Hoc

Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, 1,2Saleh Ali Alomari, 2Putra Sumari Multimedia Computing Research Group, School of Computer Science, Universiti Sains Malaysia, 11800 Penang, Malaysia [email protected], [email protected], [email protected] 1

*1,2,Corresponding Author ,

doi:10.4156/jdcta.vol5.issue6.17

Abstract In this paper proposed a caching scheme to reduce the time delay in Video on Demand (VOD) System over MANET. VOD System over MANET is an interactive multimedia system that provides video services to mobile clients. Mobile clients who use the system will encounter high service delay to watch their favorite movie and this is the main problem in this system. The proposed caching scheme is called Neighborhood-Initial Playback Based Caching Scheme (NIPBCS) to overcome the service delay in the system. In NIPBC, when a new client enters the MANET network, the Local Forwarder (LF) will detect the new client upon arrival and will send the 1st segment of a movie to the new client’s First buffer. The new client can request for the 1st segment of its favorite movie by tuning in to a channel from the Staggered Broadcasting Protocol that will broadcast the 1st segment of the movie or the new client can request from the neighbors. If the new clients’ favorite movie is the same as the 1st segment of a movie sent by the LF, the client can just switch to the First Buffer and start watching the movie. By this way the aim of this caching scheme is achieved that is to reduce the time delay in VOD system over MANET. The performance of the system is evaluated through a simulation study and the extensive simulation was conducted to get the performance result of the NIPBCS. The result obtained from the simulation shows that NIPBCS reduces 10% of the time delay of the system compared to the existing caching scheme.

Keywords: VoD, MANET, NIPBCS, Staggered Broadcast 1. Introduction With the rapid development of information technology and Internet, more and more new applications emerged to challenge the way we live [1]. The advancement in wireless technology has brought a lot of benefits to private sector, public sector and for all the mobile users such as laptop user, PDA user, hand phone user and more. It helps users to transfer or share information over a distance without the use of wires and it is generally considered to be a branch of telecommunications. With the development of wireless technology such as IEEE 801.11 (WiFi) and IEEE 801.16 (WiMax), VOD System over MANET service has become very popular and many VOD service applications are emerging. Video on Demand concept and watching videos online is becoming very famous and very demanding and the number of viewers is keep increasing each and every year. There are more than 100 video search engines that can be found such as Yahoo Video, YouTube, Mega Video and there are more than 100 video sites are available online such as BrightCove, PhotoBucket, and DailyMotion for the online users to upload, download , share, and stream videos. Statistics result from the Digital Buzz website [2] and comScore website [3], shows that the average person watch videos online for per month is estimated around 182 people and YouTube website serves 1 billion videos per day with around 1.2 billion streams each day worldwide. Since the number of viewers is increasing, it encourages many researches to work on Video on Demand System over MANET network which can enable the users to join and move out from the system at any time and the most interesting part is they can download and stream their favorite movie on their mobile devices. There are a lot of research are being conducted on for Video on Demand System over MANET network and more and more techniques are introduced to improve the system’s application and quality . The development of VOD systems over MANET enable any 3G or 4G smart phone users such as iPhone and HTC EVO 4G users who are in the MANET network coverage area to request for any

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

videos which is stored in the server. The VOD system over MANET can be implemented in the airport, university, restaurants, or hotels for the mobile users to spend their time wisely while waiting to be served or while taking a break. The videos from the server will be broadcasted to the mobile clients through a broadcasting protocol where a video will be segmented and broadcasted through a dedicated channel. However most of the VOD over MANET system poses a long delay where clients have to wait for quite some time to watch video. Researchers are finding a good solution to overcome this problem to make the system a better quality by proposing many caching scheme and other protocols to be used to broadcast videos in the system such as [15][16] [17] . This paper proposes a novel caching scheme called Neighborhood-Initial Playback Based Caching Scheme (NIPBCS) for video on demand system over MANET to reduce the time delay. This paper organized as follows: section 2 related backgrounds and section 3 described the proposed work.

2. Related background This section discusses about the Video on Demand system over MANET, Staggered broadcast protocol and types of caching schemes used in VOD systems.

2.1.Video on Demand system over MANET (MobiVod) MobiVoD [4] [12] is an example of VOD System over MANET as shown in Figure 1 and this system is consist of three components, the server that stores the videos, Local Forwarders to receive videos from the server and then broadcast the videos as segments through the wireless interface card to mobile clients, and mobile clients as a subscriber who receives and watches video. MANET is known as Mobile Ad Hoc Network and the clients in the network will communicate with each other without any centralized administrator. There is no any fixed network infrastructure in the network but all the clients create a network among themselves to share or exchange the information between them [5][6]. One of the clients in the network will act as a router and all the clients are able to communicate only with the clients within its transmission radius R and meanwhile the source and destination clients can be located at a distance much higher than R [7]. The server and the Local Forwarder are interconnected via an infrastructure-based wireless network. The local forwarder provides the services to the mobile clients within the coverage area, at the same time the mobile clients can request and receive videos directly from the Local Forwarder. Staggered Broadcasting (SB) Protocol is used in this system to disseminate the video data to the mobile clients.

Figure 1. Video on Demand System architecture over Mobile Ad hoc Network

2.2. Staggered Broadcast Protocol Staggered Broadcasting (SB) [8] [9] [10] is a simple periodic broadcast technique that is very famously used in VOD system. A video will be partitioned into K equally sized segments and the duration of each segment is calculated as s= V/K, where V is the duration of entire video and r is the

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

video consumption rate. Then the server bandwidth is divided into K equal channels and each channel repeatedly will broadcast the video with transmission rate equal to consumption rate. This protocol requires the client to join only 1 channel as shown in Figure 2. Mobile clients who are in the local forwarder’s coverage area can join the channels to receive the broadcasted segments of videos and can start watching the movie.

Figure 2. Staggered Broadcast Protocol

2.3. Caching Schemes Caching schemes are introduced in the VOD over MANET to reduce the time delay, bandwidth reduction, request rejection and to save caching space in the system. There are many caching schemes proposed by the researchers such as: 2.3.1.

2.3.2.

2.3.3.

2.3.4.

2.3.5.

2.3.6.

Partial Video Sequence (PVS) caching scheme [13], it decomposes video sequences into a number of parts by using a scalable video compression algorithm. Video parts are selected to be cached in local video servers based on the amount of bandwidth that would be demanded from the distribution network and central video server if it was only kept in the central video server. PVC caching improves the performance of caching, provides more reduction in the bandwidth requirement than the conventional caching scheme. Prefix Caching [11], it could reduce the request rejection ratio and client waiting time. The network bandwidth usage also has been reduced by the caching scheme through sharing the video data of the currently played video object with other clients of the active chain. Dominating-Set Cache (DSC) [4] In DSC, when a new client X is in the transmission range of existing client Y and the client is not forwarding cache to any other client, client X can make use of the cache at Y and plays the video. But if client X is not in the transmission area of client Y, the client Y will find another client Z who shares the same transmission area with itself and client X, Y will download the broadcast portion that x misses from Z and forwards it to X. Random Cache [4], simplest selective cache algorithm and only a number of selected clients are allowed to cache the first segment of a video. The advantage of this caching scheme is the saving on caching space and the disadvantage is it has the higher service delay. Client Caching Scheme for Interactive Video- on-Demand [14], it is used to reduce the traffic load on the network where a local client will cache a video and when the video once retrieved from the server, it will be retained in a video cache on the client for the remainder of the session. If other clients want to watch the same video again, the video can be viewed from the cache and not from the server. If the local cache is full, an aging mechanism is used to decide which frame is to be overwritten by the most recently requested one. Neighbor Based Caching Scheme, Mobile client can download the first segment of the video from the initial buffer of the neighbor client to its own initial buffer [14]. The mobile client must be within the coverage area of neighbor client. When the initial buffer of the mobile client is filled with the first segment downloaded from the neighbor client, now it will acts as the self based caching scheme and broadcasts the segment like how the Self based caching system does.

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

3. Neighborhood Initial-Playback Based Caching (NIPBC) Scheme The caching scheme proposed in this paper is called as Neighborhood Initial-Playback Based Caching Scheme (NIPBC). The purpose of this caching scheme is to receive the 1st segment of a movie from the local forwarder and to make sure all the clients in the MANET network area to have the 1st segment of (movie j) from the closer local forwarder. In this case, the mobile clients will save the first segment received from the local forwarder in the First-Buffer. Besides that this approach makes it easy for the mobile clients to request for the 1st segment of a (movie j) from the neighbors because the probability of neighbors having the 1st segment of any movie is very high. The novel scheme NIPBC is able to reduce waiting time or the service latency of the mobile client in the VOD System over MANET compared to other caching schemes.

3.1. Features of Mobile Client Mobile clients involved in this research are 3G or 4G smart user phones because this type of mobile clients can download and playback the videos to their handphones. The memory card of these mobile clients is divided into three buffers, First buffer, Initial Buffer, and Pre-fetched buffer and these buffers are used to cache the segments of the whole movie either from the Local Forwarder or from neighbor clients. The First buffer is to store the 1st segment of a movie that was sent by the Local Forwarder. The Initial buffer is to cache the 1st segment of a movie from the Staggered Broadcasting Protocol or from the neighbors meanwhile Pre-fetched buffer is to cache the second segment and the following segments of the movie. The size of First buffer and Initial buffer is equal to the size of the 1st segment of a movie meanwhile the size of the pre-fetched buffer is larger than both buffers. Figure 3 shows the features of smart phone with 3 buffers.

Figure 3: The feature of mobile client with 3 buffers.

3.2. Features of Neighborhood Initial-Playback Based Caching Scheme The main problem in video on demand system over MANET is the time delay that is caused by the Staggered Broadcasting Protocol. The time delay occurs when the mobile client missed the first segment of a movie that was broadcasted by the Staggered Broadcasting Protocol. If the mobile client wants to download and playback the first segment, the client has to wait until the broadcasting protocol broadcast the same segment again. Hence, NIPBCS is used to reduce the viewer’s waiting time. In the NIPBCS, when a new mobile client enters the network area, the Local Forwarder will detect the client automatically. Once the client is detected, the 1st segment of a movie that has not been sent to any other client’s first buffer will be sent to the new client. The 1st segment will be saved in the First buffer of the mobile. By sending the 1st segment of a movie to the First buffer of the new client, it ensures that all the clients in the MANET environment will have the 1st segment of all the movies that is stored in the Local Forwarder. The architecture of the NIPBCS is shown in Figure 4.

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

Figure 4. Mobile client E after entering the network in NIPBCS

4. The Scenarios of the simulation model The steps to detect the arrival of mobile client and the distribution of 1st segment by the Local Forwarder used in this caching scheme are shown below, where U1 as the new mobile client, LF1 as the Local Forwarder:

4.1. Detection procedure for the arrival of mobile client The procedure to detect the arrival of the new client and distribution of 1st segment of a movie by LF: 1. U1 enters the network 2. LF1 detects the arrival of U1 3. LF1 checks which movie’s 1st segment is not in other client’s first buffer. 4. If all the movie’s 1st segment is in all the other client’s 1st buffer  LF1 will send again 1st segment of any movie to U1 5. Else if there is a movie’s 1st segment is still not sent  LF1 will chose that movie’s 1st segment to be sent to U1 6. LF1 sends a message to the U1 to accept the 1st segment. 7. LF1 sends the 1st segment to U1’s 1st buffer. 8. U1 accepts the 1st segment. Figure 5 shows that mobile client E has arrived to the network at time t0+s and as in the Staggered Broadcasting Protocol schedule; it has already broadcasted the 1st segment of movie 2 at time t0. In this case, client E could not cache the first segment to its initial buffer because it already missed the first segment. Thus in order to watch the movie, the client has to wait until the Staggered Broadcasting Protocol broadcast the same segment again at the same channel or to another channel that broadcast the same 1st segment the soonest. Waiting for the broadcasting protocol to broadcast the first segment again will consume more time for the client, hence without wasting any time the client can request from its neighbors who have the first segment of movie 2 for example Mobile Client B as shown in Figure 5. Mobile client B will send the first segment of movie 2 from its First buffer to client E as long as it is still in the Local Forwarder transmission area and is not transmitting any segment of video to any other client.

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

Figure 5: Mobile client A requesting 1st segment of Movie 2 from mobile client B and caching 2nd segment and the following segments to its pre-fetched buffer. The scenarios of the Playback procedure shown below to explain how the IPBCS works:

4.2. First scenario of the Play Back Procedure Scenario of playback procedure where the mobile client (U1) already have the first segment of a movie A in its First Buffer: 1. 2. 3. 4. 5. 6. 7. 8.

LF detect mobile client U1 LF send message followed by S1 to U1 First Buffer U1 request 1st segment of movie 1  If First Buffer have the same 1st segment of movie 1 U1 will playback the 1st segment from the First Buffer. At the same time U1 join the broadcasting channel to receive the rest of segments in the prefetched buffer. After U1 finish viewing the 1st segment will switch to the pre-fetched buffer. Quit the channel. Else use the Second scenario of the Play Back Procedure.

4.3. Second scenario of the Play Back Procedure Scenario of playback procedure of mobile client U1 caching first segment from broadcasting channel: 1. Detect local forwarder 2. Find the channel from local forwarder which is going to broadcast the S1 soonest 3. Wait and join that channel 4. Download the S1 in its initial_play buffer and cache remaining segments into pre-fetched buffer. 5. Play S1 in initial_play buffer and switch to pre-fetched buffer to play remaining segments. 6. Quit the channel.  

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

4.4 Third scenario of the Play Back Procedure Scenario of playback procedure mobile client U1 when missed the first segment (S1) of the video: 1. U1 send request for S1 from neighbors who in the same area network of U1 2. U2 within the network area 3. U2 currently are not forwarding first segment to other mobile user 4. If such U2 exist  Download S1 from U2 into U1’s initial_play buffer  The U1 join the broadcasting channel and save the remaining segments of the video. 5. If download is complete  U1 play data in its initial_play buffer  After play the S1, U1 switch to pre-fetched buffer to play remaining segments of the video. 6. Else If such U2 does not exist 7. Detect a local forwarder 8. Find the channel from local forwarder which is going to broadcast the S1 soonest 9. Wait and join that channel 10. Download the S1 in its initial_play buffer and watch remaining segments from pre-fetched 11. Quit the channel.

5. Simulation Parameters Each simulation runs for T = 24 hours during which the mobile clients join the service area with arrival times and Table 1 shows the parameters used in the simulation. Parameter Service area radius \ Client Transmission Simulation period Client arrival rate Moving probability Maximum moving distance Video length Fail rate probability Number of broadcast channels Video Consumption Rate Number of Video Bandwidth

Notation MoveMAx Pmove Carrival Tsimulation Cradius Dradius L Pfail K r N B

Default Value 100m 20m 24 hours 6 clients/min 0.2 1m 60 minutes 2 and 10 5 1.5 5 54Mbps

Value Range N/A N/A N/A {2,4,6,8,10} {0.0, 0.1,0.2,0.3,0.4} N/A {60} {2, 4, 6, 8 and10} N/A N/A N/A N/A

Table 1. Simulation parameters

6. Simulation Model Figure 6(a), 6(b) and 6(c) shows the simulation visualization of the Neighborhood Initial-Playback Based Caching Scheme (NIPBCS) on VOD System over MANET.

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

Figure 6(a). Simulation model when the both client reply the request

Figure 6(b). Simulation model when client 1 only reply the request

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Video on Demand Caching System using NIPBCS over Mobile Ad Hoc Network Vaithegy Doraisamy, Saleh Ali Alomari, Putra Sumari International Journal of Digital Content Technology and its Applications. Volume 5, Number 6, June 2011

Figure 6(c). Simulation model when both of the clients not reply the request Table 2 shows the arrows used in the simulation visualization and the explanation of each arrow Arrow

And Project attractiveness is Sending message to the new client to accept the 1st segment and then send the 1st segment to its First buffer Sending acknowledgement to the Local Forwarder upon receiving the 1st segment Request for 1st of M1 from Local Forwarder If the client request time is equal to t0, client [i] can tune in to channel 1 If client request time is equal to t0+s+3, LF send message with information about neighbor with M1 1st segment with its position to Client[i]. Sending request to neighbors with the 1st segment and neighbors replying the request to Client [i] When twait=tdelay, Client[i] tune in to channel 2 Table 2. The arrows used in simulation visualization and explanation

Steps on how a new client can receive the 1st segment of a movie. 1) First the Local Forwarder will detect the arrival of the new client and will send a message to the client to accept the 1st segment and then will send the 1st segment to the client’s first buffer. Client_Detect : LFposition - Client_iposition