Codebook-based Beamforming Research Articles

IEEE 802.15.3c: the first IEEE wireless standard for data rates over 1 Gb/s

This article explains the important features of IEEE 802.15.3c, the first wireless standard from IEEE in the 60-GHz (millimeter wave) band and its development. The standard provides three PHY modes for specific market segments, with mandatory data rates exceeding 1 Gb/s. During the span of the standard development, new contributions to wireless communication technology were also made, including a new channel model, a codebook-based beamforming scheme, and a low-latency aggregation method.

Codebook-based opportunistic beamforming for downlink multiple input multiple output systems

Opportunistic beamforming (OBF) is an efficient technique to exploit multiuser diversity in static channel environments. Since the OBF experiences lack of diversity when user population is low, a codebook-based opportunistic beamforming (COBF) is proposed. The COBF allows users to choose the best beam among multiple random beams. The COBF uses fixed pilots for channel estimation and generates multiple random beams by using a codebook composed of multiple fixed beams and a random matrix altering the beams with time slots. Compared with the conventional multi-beam opportunistic beamforming (MOBF), which also provides the beam selection diversity to the OBF, the number of beams in the COBF is related to the size of codebook, not the number of pilots. Accordingly, the COBF can increase the beam selection diversity without a restriction of pilot overhead. When the COBF is extended to a system that transmits multiple data streams in a time slot, the system throughput improvement over the OBF and the MOBF grows as the number of streams is increased because the pilots can be saved further.

An upper bound on the SER of transmit beamforming in correlated rayleigh fading

We study the symbol error rate (SER) of maximum ratio transmission, transmit antenna selection, and codebook-based beamforming in correlated Rayleigh fading channels. Assuming maximum ratio combining is performed at the receiver, we derive a universal upper bound on the average SER of the three schemes, and prove that the bound is asymptotically tight in high signal-to-noise ratio (SNR) regions. However, numerical results show that at medium SNR, the tightness of the bound depends on the condition number of the channel correlation matrix.

Beamforming in MISO Systems: Empirical Results and EVM-Based Analysis

We show that efficient implementation of codebook-based beamforming Multiple Input Single Output (MISO) systems with good performance is feasible in the presence of channel-induced imperfections (due to imperfect channel estimate and feedback delay) and implementation-induced imperfections (due to real-world radio hardware effects). To present our results, we adopt a mixed approach of analytical, simulation, and experimental evaluation. Our analytical and simulation results take into account channel-induced imperfections but do not take into account implementation-induced imperfections (which are difficult to model in a tractable way). Thus, we complement these results with experimental results that do take into account both channel and implementation-induced imperfections. This mixed approach provides a more complete picture of expected performance. As part of our study we develop a framework for Average Error Vector Magnitude Squared (AEVMS)-based analysis of beamforming MISO systems which facilitates comparison of analytical, simulation, and experimental results on the same scale. In addition, AEVMS allows fair comparison of experimental results obtained from different wireless testbeds. We derive novel expressions for the AEVMS of beamforming MISO systems and show how the AEVMS relates to important system characteristics like the diversity gain, coding gain, and error floor.