Hybrid MIMO Architectures for Millimeter Wave Communications: Phase Shifters or Switches?

Abstract

Hybrid analog/digital MIMO architectures were recently proposed as an alternative for fully-digitalprecoding in millimeter wave (mmWave) wireless communication systems. This is motivated by the possible reduction in the number of RF chains and analog-to-digital converters. In these architectures, the analog processing network is usually based on variable phase shifters. In this paper, we propose hybrid architectures based on switching networks to reduce the complexity and the power consumption of the structures based on phase shifters. We define a power consumption model and use it to evaluate the energy efficiency of both structures. To estimate the complete MIMO channel, we propose an open loop compressive channel estimation technique which is independent of the hardware used in the analog processing stage. We analyze the performance of the new estimation algorithm for hybrid architectures based on phase shifters and switches. Using the estimated, we develop two algorithms for the design of the hybrid combiner based on switches and analyze the achieved spectral efficiency. Finally, we study the trade-offs between power consumption, hardware complexity, and spectral efficiency for hybrid architectures based on phase shifting networks and switching networks. Numerical results show that architectures based on switches obtain equal or better channel estimation performance to that obtained using phase shifters, while reducing hardware complexity and power consumption. For equal power consumption, all the hybrid architectures provide similar spectral efficiencies.

Low Cost and High Efficiency Hybrid Architecture Massive MIMO Systems Based on DFT Processing

“…This observation confirms the derived analytical expressions in Theorem 2 and Corollary 3. Meanwhile, Figure 2 also provides the total achievable SE for the full digital architectures [43], as well as the hybrid architectures with the ideal phase shifters and switch network [19]. It is shown that the total achievable SE of full digital architectures always outperforms the one of hybrid architectures, regardless of ideal phase shifters, switch network, and DFT precessing.…”

“…The detailed energy consumption is provided by LAN = 20 × 10 −3 Watt, PS = 30 × 10 −3 Watt, SW = 5 × 10 −3 Watt, FR = 40 × 10 −3 Watt, cod = 4 Watt, and dec = 500 × 10 −3 Watt, and assume that the efficiency of transmitter power is = 0.5 at the BS. These above parameters are obtained from the results of [19,37] for hybrid architectures. Figure 5 displays the total achievable EE as a function of the input SNR.…”

“…Before depicting the total achievable EE, we shall present the energy consumption for full digital architecture, hybrid architectures with ideal phase shifters, and switch network hybrid architectures because the energy consumption of hybrid architectures with DFT processing has been provided in Section 3. With the help of the energy consumption models that have been provided in [19,37,44], we know that, for full digital architecture, hybrid architectures with ideal phase shifters, and switch network hybrid architectures, the energy consumption of the signal processing part and the signal transmission part is the same as the hybrid architectures with DFT processing, and only the energy consumption of the circuit part has changed drastically. For full digital architecture, the energy consumption of the circuit part is provided by [44] …”

“…For a hybrid architecture massive MIMO system based on ideal phase shifters and switch network, the energy consumption of circuit part is provided by [19] …”

“…However, all the aforementioned studies are based on the ideal phase shifters at the analog domain, which has a potential to enhance the complexity of the system, especially for a huge quantity of data. In order to simplify the complexity of system, the work of [19] proposed hybrid architecture with a switches network, where the ideal phase shifters are replaced by a switches network. Results reported that the switches network is a simpler solution but suffers from the significantly performance loss of the system.…”