Improved Rate-Compatible Joint Network-Channel Code for the Two-Way Relay Channel

In [1] a rate-compatible joint network-channel code (JNCC) for the two-way relay channel was proposed which can be applied for the cooperative uplink and downlink in a mobile communication system with the help of a relay. We assume the system model of [1] and present an improved JNCC which is based on the decode-and-forward scheme of [2]. In [2] a coding scheme was proposed which does not consider that the base station can also listen to the transmission of the mobile station and vice versa. We extend this scheme to a distributed coding scheme with hybrid automatic repeat request/forward error correction (H-ARQ/FEC) such that the transmission between mobile and base station can be also exploited. Due to the wireless broadcast nature, this transmission is for free. Fig. 1 depicts the channel encoder which is used at mobile and base station. It contains the same parallel concatenated convolutional code (PCCC) as in [1] with information bit block length K = 1500 and a H-ARQ/FEC functionality. The N = 4512 code bits are arranged according to the order described in [1]. Packets of M = 600 code bits are (re)transmitted from the mobile/base station until the relay or the base/mobile station can decode without error. If the relay has decoded the data of the mobile and base station correctly and one of the two stations requires still more retransmissions, the relay network encodes the estimates ûMR and ûBR and broadcasts the network code bits xR to mobile and base station. The network encoder is depicted in Fig. 2 (a). It differs from the one in [1]. The H-ARQ/FEC functionality chooses the bits according to the same order as the channel encoder. However, it starts from the position where the channel encoders stopped to