Downlink Multicell Processing with Limited-Backhaul Capacity

Abstract

Multicell processing in the form of joint encoding for the downlink of a cellular system is studied under the assumption that the base stations (BSs) are connected to a central processor (CP) via finitecapacity links (finite-capacity backhaul). To obtain analytical insight into the impact of finite-capacity backhaul on the downlink throughput, the investigation focuses on a simple linear cellular system (as for a highway or a long avenue) based on theWyner model. Several transmission schemes are proposed that require varying degrees of knowledge regarding the system codebooks at the BSs. Achievable rates are derived in closed-form and compared with an upper bound. Performance is also evaluated in asymptotic regimes of interest (high backhaul capacity and extreme signal-to-noise ratio, SNR) and further corroborated by numerical results. The major finding of this work is that even in the presence of oblivious BSs (that is, BSs with no information about the codebooks) multicell processing is able to provide ideal performance with relatively small backhaul capacities, unless the application of interest requires high data rate (i.e., high SNR) and the backhaul capacity is not allowed to increase with the SNR. In these latter cases, some form of codebook information at the BSs becomes necessary.

Joint optimization of cloud and edge processing for fog radio access networks

“…The signalsx i andx j for different eRRHs i = j are quantized independently so that the quantization noise signals q i and q j are independent [5] 3 .…”

Transmit beamformer and quantization design for multi-carrier CRAN CoMP

“…Now, the optimization variable t k,n in (4) is determined by the SINR γ k,n , which in turn depends on the transmit beamformers by (2). In order to ensure that c b,k,n determines whether BS b is serving user k over a sub-channel n or not, the binary variable c b,k,n should be coupled with the respective beamformer as…”

“…Therefore, it is not always beneficial to share the data of all users in the system to all BSs. In such cases, the beamformer design becomes a more challenging problem as it involves both user association and the beamformer design for the chosen subset of users [2]- [4]. Downlink transmission is primarily focused on satisfying certain quality-of-service (QoS) imposed by the higher layers based on the user service category.…”

Joint multi-cell processing for downlink channels with limited-capacity backhaul

“…As pointed out in [14], in order to implement the sequential DPC scheme correctly, we need to "turn off" every (J + 2)th BS (e.g., BSs J + 2, 2(J +2), ...) and consider the clusters of J +1 BSs in between silent BSs. Details can be found in [15].…”

“…(12) Proof : See [15]. In absence of constraints on the backhaul, C → ∞, unlike R 1 and R 2 , the scheme proposed above achieves the upper bound (2) R 3 → R ub (sinceP → P ).…”