Wireless network cocast: location-aware cooperative communications with linear network coding

Abstract

Abstract-In wireless networks, reducing aggregate transmit power and in many cases, having even power distribution increase the network lifetime. Conventional direct transmission (DTX) scheme results in high aggregate transmit power and uneven power distribution. In this paper, we consider location-aware cooperation-based schemes namely immediate-neighbor cooperation (INC), maximal cooperation (MAX), and wireless network cocast (WNC) that achieve spatial diversity to reduce aggregate transmit power and even power distribution. INC utilizes twouser cooperative communication, resulting in good reduction of aggregate transmit power and low transmission delay; however, power distribution is still uneven. MAX utilizes multi-node cooperative communication, providing incremental diversity to achieve even power distribution and substantial reduction in aggregate transmit power. Transmission delay in MAX, however, grows quadratically with network sizes. As a result, the novel WNC is proposed to achieve incremental diversity as in MAX and low transmission delay as in INC. In WNC, mobile units acting as relays form unique linearly-coded signals from overheard signals and transmit them to the destination, where a multiuser detector jointly detects the symbols from all received signals. Performance evaluation in uniformly distributed networks shows that INC, MAX, and WNC substantially reduce aggregate transmit power while MAX and WNC also provide even power distribution.

Space-time network coding

“…Location-aware WNC that considers node locations to reduce aggregate transmit power in a network and achieve even power distribution among the nodes was studied in [16]. The corresponding STNC, which is a special case of that in Fig.…”

“…In this work, we leverage a novel concept of wireless network cocast (WNC) [16] and propose its associated space-time network codes (STNCs) to achieve the foretold objectives. Cocast, an abbreviation of cooperative cast, is a newly defined transmission method, in which information from different nodes are jointly combined within a relay and transmitted to the intended destinations.…”

Coalition formation games for energy-efficient wireless network cocast

“…The additional processing power linearly increases with the size of the cooperative group. However, the transmit power saving in cooperation gradually diminishes due to the nature of incremental diversity that causes the relative transmit power saving to reduce [9]. At some point, user nodes can no longer be added to the cooperative group.…”

Differential Space-Time Network Coding for Multi-Source Cooperative Communications

“…However, if space-time block codes are used in [10], the transmission rates of [10] and [11] decrease as the number of relays increases. Full-diversity multisource cooperation protocols have been proposed in [12] and [13] cocast (WNC) and space-time network coding (STNC) have been proposed by leveraging the idea of network coding in [14] and [15]. WNC in [14] can provide incremental diversity, while the STNC scheme in [15], which combines symbols in code division multiple access (CDMA) or frequency division multiple access (FDMA) mode at each relay, can solve the imperfect synchronization issue and achieve full diversity.…”

“…Compared to 2 time slots for a traditional TDMA-based cooperative communication network of nodes [5], this is a substantial reduction in transmission delay. However, in both [14] and [15], extra frequency resource is required.…”