Performance Bounds for Bi-Directional Coded Cooperation Protocols

Abstract

Abstract-In coded bidirectional cooperation, two nodes wish to exchange messages over a shared half-duplex channel with the help of a relay. In this correspondence, we derive performance bounds for this problem for each of three decode-and-forward protocols. The first protocol is a two phase protocol where both users simultaneously transmit during the first phase and the relay alone transmits during the second. In this protocol, our bounds are tight. The second protocol considers sequential transmissions from the two users followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. In the latter two protocols the bounds are not identical. Numerical evaluation shows that in some cases of interest our bounds do not differ significantly. Finally, in the Gaussian case with path loss, we derive achievable rates and compare the relative merits of each protocol. This case is of interest in cellular systems. Surprisingly, we find that in some cases, the achievable rate region of the four phase protocol contains points that are outside the outer bounds of the other two protocols.

Capacity Scaling for MIMO Two-Way Relaying

“…This idea is reminiscent of network coding [28], though note that here the coding is done in analog domain rather than in digital domain. The MIMO two-way relay channel is also known by several other names in the literature, namely, bidirectional MIMO relay channel [24] and is also a special case of analog network coding [28].…”

“…packet acknowledgements from the destination to the source, downlink and uplink in cellular networks. Consequently, there has been interest in the two-way relay channel, where the bidirectional nature of communication is taken into account [21]- [24]. The two-way relay channel was studied in [22], where upper and lower bounds on the capacity region were derived for a general discrete memoryless channel.…”

“…In prior work, achievable rate region (region enclosed by the rates achievable on the T 1 → T 2 and T 2 → T 1 links, simultaneously) expressions were derived for the Gaussian half-duplex MIMO two-way relay channel (fading coefficients as well as additive noise is Gaussian distributed) using AF [21] and DF [23], [24] at the relay node. A main conclusion derived in prior work [21], [23], [24], is that it is possible to remove the 1 2 rate loss factor in spectral efficiency due to the half-duplex assumption on the relay node.…”

Cost sharing with network coding in two-way relay networks

“…It has become well established that network coding [1] can improve the throughput of such a two-way relay over traditional storeand-forward routing, e.g. see [2], [3]. In many cases, the use of a relay node will incur a cost, for example representing the energy consumption of the relay.…”

Resource-efficient wireless relaying protocols

“…3d, the RS performs FEC decoding in order to mitigate the effects of error propagation. A possible approach [4,11] not depicted here for the two-phase DF relaying protocol is that the RS separately decodes the codewords c 1 and c 2 , which are transmitted from the MS and BS, respectively. The RS receives the superposition of the UL and DL signals in the first phase and attempts to decode both of them.…”