Current Issue : April - June Volume : 2018 Issue Number : 2 Articles : 5 Articles
Channel change time is a critical quality of experience (QOE) metric for IP-based video delivery systems such as Internet Protocol\nTelevision (IPTV). An interesting channel change acceleration scheme based on peer-assisted delivery was recently proposed,which\nconsists of deploying one FCC server (Fast Channel Change Server) in the IP backbone in order to send the unicast stream to the\nSTB (Set-Top Box) before sending the normal multicast stream after each channel change. However, deploying such a solution will\ncause high bandwidth usage in the network because of the huge unicast traffic sent by the FCC server to the STBs. In this paper,\nwe propose a new solution to reduce the bandwidth occupancy of the unicast traffic, by deploying the FCC server capabilities\non the user STB. This means that, after each channel change request, the STB will receive the unicast traffic from another STB\ninstead of the central server. By using this method, the unicast traffic will not pass through the IP network; it will be a peer-to-peer\ncommunication via the Access Network only. Extensive simulation results are presented to demonstrate the robustness of our new\nsolution...
Digital multimedia broadcasting signal is promised to be a wireless positioning signal.\nThis paper mainly studies a multimedia broadcasting technology, named China mobile multimedia\nbroadcasting (CMMB), in the context of positioning. Theoretical and practical analysis on the CMMB\nsignal suggests that the existing CMMB signal does not have the meter positioning capability.\nSo, the CMMB system has been modified to achieve meter positioning capability by multiplexing the\nCMMB signal and pseudo codes in the same frequency band. The time difference of arrival (TDOA)\nestimation method is used in base station positioning receivers. Due to the influence of a complex\nfading channel and the limited bandwidth of receivers, the regular tracking method based on pseudo\ncode ranging is difficult to provide continuous and accurate TDOA estimations. A pseudorange\nmeasurement scheme based on snapshot is proposed to solve the problem. This algorithm extracts\nthe TDOA estimation from the stored signal fragments, and utilizes the Taylor expansion of the\nautocorrelation function to improve the TDOA estimation accuracy. Monte Carlo simulations and\nreal data tests show that the proposed algorithm can significantly reduce the TDOA estimation\nerror for base station positioning receivers, and then the modified CMMB system achieves meter\npositioning accuracy....
A wireless sensor network (WSN) is emerging as an innovative method for gathering\ninformation that will significantly improve the reliability and efficiency of infrastructure systems.\nBroadcast is a common method to disseminate information in WSNs. A variety of counter-based\nbroadcast schemes have been proposed to mitigate the broadcast-storm problems, using the count\nthreshold value and a random access delay. However, because of the limited propagation of\nthe broadcast-message, there exists a trade-off in a sense that redundant retransmissions of the\nbroadcast-message become low and energy efficiency of a node is enhanced, but reachability\nbecome low. Therefore, it is necessary to study an efficient counter-based broadcast scheme that can\ndynamically adjust the random access delay and count threshold value to ensure high reachability,\nlow redundant of broadcast-messages, and low energy consumption of nodes. Thus, in this paper,\nwe first measure the additional coverage provided by a node that receives the same broadcast-message\nfrom two neighbor nodes, in order to achieve high reachability with low redundant retransmissions\nof broadcast-messages. Second, we propose a new counter-based broadcast scheme considering the\nsize of the additional coverage area, distance between the node and the broadcasting node, remaining\nbattery of the node, and variations of the node density. Finally, we evaluate performance of the\nproposed scheme compared with the existing counter-based broadcast schemes. Simulation results\nshow that the proposed scheme outperforms the existing schemes in terms of saved rebroadcasts,\nreachability, and total energy consumption...
The model for a broadcast channel with confidential messages (BC-CM) plays an important\nrole in the physical layer security of modern communication systems. In recent years, it has been\nshown that a noiseless feedback channel from the legitimate receiver to the transmitter increases\nthe secrecy capacity region of the BC-CM. However, at present, the feedback coding scheme for\nthe BC-CM only focuses on producing secret keys via noiseless feedback, and other usages of the\nfeedback need to be further explored. In this paper, we propose a new feedback coding scheme\nfor the BC-CM. The noiseless feedback in this new scheme is not only used to produce secret keys\nfor the legitimate receiver and the transmitter but is also used to generate update information that\nallows both receivers (the legitimate receiver and the wiretapper) to improve their channel outputs.\nFrom a binary example, we show that this full utilization of noiseless feedback helps to increase the\nsecrecy level of the previous feedback scheme for the BC-CM....
We consider the training design and channel estimation in the amplify-and-forward (AF) diamond relay network. Our strategy is\nto transmit the source training in time-multiplexing (TM)mode while each relay node superimposes its own relay training over the\namplified received data signalwithout bandwidth expansion.Theprincipal challenge is to obtain accurate channel state information\n(CSI) of second-hop link due to the multiaccess interference (MAI) and cooperative data interference (CDI). To maintain the\northogonality between data and training, a modified relay-assisted training scheme is proposed to migrate the CDI, where some\nof the cooperative data at the relay are discarded to accommodate relay training. Meanwhile, a couple of optimal zero-correlation\nzone (ZCZ) relay-assisted sequences are designed to avoid MAI. At the destination node, the received signals from the two relay\nnodes are combined to achieve spatial diversity and enhanced data reliability.The simulation results are presented to validate the\nperformance of the proposed schemes....
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