Transmit Beamforming Analysis for MIMO Systems in Indoor Residential Environment Based on 3D Ray Tracing

Abstract

International audienceIn this paper, an evaluation of transmit beamforming (TxBF) contribution is analyzed in the context of an indoor residential environment. Using an optimized 3D ray tracing tool, the multiple-input multiple-output (MIMO) propagation channel is simulated. The algorithm of singular value decomposition is applied and a new transmission scheme is considered. Comparisons of cases with/without TxBF are realized by analyzing the received power, the signal to noise ratio (íµí±†íµí±íµí± ) of each spatial stream and the channel capacity. It is shown that the TxBF capacity gain increases when the MIMO channel correlation at the transmit side reaches high values, especially when only the dominant eigen mode is selected. The main result concerns the antenna spacing: a judicious choice of the transmitting antenna spacing can improve the effective transmission range by more than 45% in non-line of sight (NLOS) conditions. Several MIMO configurations (number of antennas and spatial streams) are also compared to determine the relevance of a possible activation of TxBF. The interference influence is studied and it is shown that under some conditions, TxBF improves the signal to interference ratio (SIR)

Impact of EIRP Constraint on MU-MIMO 802.11ac Capacity Gain in Home Networks

“…The BD method consists first of perfectly suppressing the inter-user interference (IUI) (IUI = ∑ in order to have parallel SU-MIMO systems. Then, a classic TxBF is applied to optimize the capacity for each user [9]. In this study, we set K = 2, but the results and algorithms can be generalized to any K number of users.…”

“…The considered SU-MIMO system applies a singular value decomposition and its capacity is computed as detailed in [9] for each OFDM subcarrier.…”

“…A Matlab source code [11] was used to compute the different 802.11ac TGac-B channel samples over a 20 MHz bandwidth. To have representative results, 100 couples of users (K = 2) are randomly drawn around the access point following the IEEE TGac recommendations [9]. For each drawing, we use a simulation length equal to 55 coherence times of the MIMO channel to simulate the fading.…”

IEEE 802.11ac multi-user MIMO capacity and impact of antenna array geometry based on indoor measurements

“…For the corresponding SU-MIMO systems and for relevant comparisons with MU-MIMO, the numbers of transmitting antennas n T and receiving antennas n R k remain unchanged. The considered SU-MIMO system applies a singular value decomposition and its capacity is computed for each OFDM subcarrier as detailed in [4]. We denote C 1 and C 2 the provided capacities for two users respectively.…”

“…Thus, with perfect Channel State Information (CSI) at the Transmitter (Tx), BD transforms a MU-MIMO system into several parallel Single User MIMO (SU-MIMO) systems after canceling the IUI. Transmit eigenbeamforming [4] is then applied to maximize capacity. In fact, when a perfect CSI is provided at the access point, zero IUI is achievable at every receiver, enabling thereby a simple receiver at each user.…”