Improved transmit null steering for MIMO-OFDM downlinks with distributed base station antenna arrays

Zhang

et al. 2012

Int J Communication

SUMMARYFemto cell technology is a promising solution for indoor coverage of cellular systems. The interference between macro and femto cells can be mitigated via cooperation between the macro base station (BS) and the inside femto sites (FSs). In this paper, the idea of multi-cell multi-input and multi-output is introduced, whereby the macro BS shares the same frequency band with the inside FSs in support of the femto users. Both single-user and multi-user precoding at the macro BS are proposed to support the cooperative transmission between the macro BSs and FSs. In single-user precoding and multi-user precoding without power allocation, only the angle information of the FS-user channels is required to be sent from the users to the macro BS. If the magnitude information is also sent by each user, multi-user precoding with power allocation can be employed to support cooperation between macro BSs and FSs, which is an extension of the classical water-filling optimization problem. Theoretical derivations and an iterative algorithm are both presented to solve this optimization problem. Analytical and simulation results with respect to the signal received with interferences validate the effectiveness of cooperation between the macros BSs and FSs.

Section: H Long Et Almentioning

confidence: 99%

Section: H Long Et Almentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Precoding and channel state information sharing in cooperative macro base stations and femto sites

Long

Zhang

et al. 2012

Int J Communication

“…The topics include from capacity [6,7], joint processing [8][9][10], location optimization [11] to those considering the practical imperfect conditions such as backhaul constraints [12] and asynchronous interference [13].…”

Section: Related Studymentioning

confidence: 99%

“…In these study, however, each user connects with only one RRH port, which simplifies the PCPP. In [8], an improved null steering downlink OFDMA-RRH system is proposed which reduces both the inter-user correlation and the near-far problem resulting in a significant enhancement, but the PA therein is not jointly optimal. Our previous study in [18] addresses the joint problem to maximize system SE, but the assumption is made that subcarriers are assigned by the round robin method.…”

Section: Related Studymentioning

confidence: 99%

Joint resource allocations for remote radio head deployments with coherent transmitter

Shi

et al. 2012

J Wireless Com Network

To deal with the future high demands of wireless traffic and energy consumption, one type of heterogeneous deployments is to distribute the base station antennas throughout the entire cell, which is called remote radio head (RRH). In view of radio resource management, the joint resource allocation in broadband orthogonal frequency division multiple access RRH (OFDMA-RRH) has not been thoroughly studied, which includes the antenna port selection, subcarrier assignment and power allocation under the power constraints per antenna port. This article focuses on the downlink resource allocation in OFDMA-RRH, where the coherent transmitter with phase steering is used. The problem to maximize the system spectrum efficiency (SE) is formulated, and solved by a dual decomposition method, where the decomposed sub-problems in the dual domain are solved by analytic geometry. In the optimal solution, the system power is always exhaustively used. As another contribution, this article further proposes that in the optimal solution, there is a considerable part of system power which makes little contribution to the SE and thus should be saved. Specifically, the energy efficiency is analyzed for an individual subcarrier transmission. A proportional power allocation (PPA) method is proposed to achieve a local optimality for each subcarrier. By applying the PPA to every subcarrier in order to maximize the system SE, a new resource allocation problem is formulated and solved. Discussions are also presented for the proposed algorithms on the computational complexity and feasibility in multi-cell cases. Simulation results show that the optimal algorithm consumes all the system power and has good convergence. The algorithm applying PPA can effectively improves the system power efficiency while achieving the SE optimality.

Outage Capacity Study of the Distributed MIMO System with Antenna Cooperation

Chen

Chen

2010

Wireless Pers Commun

This letter analyzes the outage capacity of the distributed multi-input multi-output (D-MIMO) systm with antenna cooperation over the Rayleigh-Log-normal fading channel. Firstly, an analytical expression of outage capacity is derived under the cooperative transmission scheme (CTS). Moreover, to optimize the system performance, an adaptive CTS (ACTS) is proposed, and a theoretical expression is derived to perform the ACTS. Simulation results are presented to verify the theoretical outcome.