A multi-antenna technique for mm-wave communications with large constellations and strongly nonlinear amplifiers

Abstract

It is well-known that mm-wave (millimeter wave) communications have high potential for future wireless broadband systems. However, there are important challenges that need to be overcome when implementing those systems, both at the hardware level and due to the hostile propagation conditions. This is especially important for spectrally efficient communications based on large constellations, since the power requirements are higher, as well as the amplification difficulties, specially for large, dense constellations.In this paper we propose a multi-antenna transmitter combined with a frequency-domain receiver for broadband mm-wave systems based on large and dense constellations. Our transmitter is compatible with highly-efficient, low-cost, strongly nonlinear amplifiers, while allowing spacial multiplexing gains. 1

Ring-type Magnitude Modulation for LINC: a pragmatic approach to the efficiency challenge

“…It is known that OQPSK signals can be used to represent any M-ary constellation [13], [26], and the transmission of several OQPSK signals in parallel using multi-layer massive MIMO transmitter schemes for high-order constellations has been recently proposed in [15], [16] to meet 5G's demanding throughput and spectral efficiency. This combined with the use of LINC techniques may leverage the development of transmitters with high power efficiency.…”

“…TRANSCEIVER SCHEME Leveraging on LINC concept and the new RMM technique proposed in the previous section for OQPSK bandlimited signals, this section presents a new power-efficient OQPSK RMM-LINC transceiver scheme, foreseen as an enabling component of multi-layer massive MIMO transmitter schemes for high-order constellations recently proposed [15], [16]. Since the RMM adjustment of each symbol increase the system's noise sensitivity, it is studied the impact of the RMM technique on the transceiver's BER performance, and it is also proposed an iterative receiver scheme [21] designed to reduce the distortion introduced by the RMM method.…”

“…The situation is significantly aggravated when large constellations (e.g., 16-QAM or 64-QAM constellations) are employed to further improve the system's spectral efficiency, and the resulting high PAPR signals may seem to limit the potential of LINC use. However, any M-ary constellation can be decomposed as a sum of several polar components [13], which can be modulated as OQPSK signals (also known as staggered QPSK [14]) and amplified and transmitted separately, eventually employing multi-layer massive antenna structures [15], [16] envisioned for 5G, enabling very efficient signal transmission provided that an efficient amplification for OQPSK signals with compact spectrum is employed.…”

Simplified and accurate BER analysis of magnitude modulated M‐PSK signals

“…MM techniques can be employed [10, 11] to further reduce envelope fluctuations of bandwidth limited satellite signals, allowing enhanced power efficiency upon transmission. Also, PSK‐type constellations combined with MM have been recently considered in the design of systems with high spectral and power efficiency for 5G and beyond, in particular the recently proposed multilayer massive multiple‐input multiple‐output (MIMO) system architecture [12–14] for transmissions at millimetre wave wavelengths. This particular architecture achieves both the power and spectral efficiency goals by leveraging on a three‐layer architecture.…”

Boosting LINC systems combiners efficiency through ring-type magnitude modulation

“…As so, the use of offset signals such as OQPSK particularly suits LINC, since it is known that these can have much lower envelope fluctuations than non-offset signals. In fact, recently, new architectures have been proposed for 5G [7], [8] employing multi-layer massive antenna structures allowing for highly power and spectral efficient transmitters leverage on the the use of large constellations (e.g., 16-QAM or 64-QAM) that are decomposed as a sum of several OQPSK-type signals [9]; these OQPSK components can individually be efficiently amplified by using LINC and transmitted separately through different antennas. However, compact spectrum OQPSK signals (e.g., trough a square-root raised-cosine filtering with small roll-off) can possess significant envelope fluctuations which may impact on LINC combiner efficiency; in fact, OQPSK-type signals can only have constant envelope at the expense of bandwidths much wider than the minimum Nyquist band (e.g.…”