Multilayer Orthogonal Beamforming for Priority-Guaranteed Wireless Communications

Abstract

To utilize the benefits of cellular systems, wireless machine-to-machine (M2M) communications over cellular systems are being widely considered. In order to support efficient spectrum sharing between M2M devices and normal mobile users, in the paper, we propose a multilayer orthogonal beamforming (MOBF) scheme for M2M communications over orthogonal frequency division multiple access (OFDMA-) based cellular systems. Using MOBF, each subcarrier in OFDMA systems could be efficiently reused by both normal mobile users and machine-type devices which are organized into multiple virtual layers. The users located in higher layers (e.g., mobile users) are not to be interfered by those in lower layers (e.g., machine devices). To improve the performance, the orthogonal deficiency (OD-) based user selection is carried out, where the intralayer fairness and quasimaximal performance can be guaranteed, simultaneously. Moreover, the signal-to-interference plus noise ratio (SINR) is investigated to measure the performance lower bound of different layers. It is demonstrated by both theoretical and numerical results that the proposed approach provides a stable SINR performance for each layer, that is, the interference free ability from lower level layers.

SDMA-Based Aeronautical Machine-to-Machine Communications under SINR Constraints

“…In general, the simulations above illustrate that the proposed ZFBF with MFS is a proper SDMA approach for 4DT services. And the ZFBF with MFS will obtain a better SDMA gain compared with OBF in [19, 20, 35].…”

“…(17) else (18) break; (19) end if (20) end for (21) = + 1; As shown in Figure 4, the SINR decreases with Δ up to Δ max , which results from the fact that the proposed SDMA highly depends on the phase accuracy of ARVs. Although a noticeable mitigation of the performance loss can been seen at the case of a large AoA error, the overall degradation of SINR is unacceptable.…”

“…As a low complexity linear beamforming approach, orthogonal beamforming [19] is able to support hierarchical priority guaranteed SDMA in M2M communications over cellular networks [20], while it may not be appropriate for aeronautical SMN-M2M communications as an equal, performance of different 4DT management services is required on safety-of-life level. Combined with a semiorthogonal users selection (SUS) scheme [21], zero-forcing beamforming (ZFBF) has been proposed in [22] to provide equitable performance for all selected users.…”

Secure Beamforming via Amplify-and-Forward Relays in Machine-to-Machine Communications

“…In addition to human-to-human (H2H) communications, an emerging technology empowering full mechanical automation (e.g., the Internet of Things and the smart grid) that may change our living styles is vigorously being developed. Such communications among machine-type devices are known as M2M communications [2][3][4]. Due to the use of machine-type devices and the broadcast nature of wireless media, privacy and security issues play an important role in wireless M2M networks.…”