OFDM for 5G: Cyclic prefix versus zero postfix, and filtering versus windowing
OFDM for 5G: Cyclic prefix versus zero postfix, and filtering versus windowing
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5G 的 OFDM：循环前缀与零后缀、滤波与加窗
DOI：
10.1109/icc.2016.7510757
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
R. Valenzuela
中科院分区：
文献类型：
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作者：
S. Venkatesan;R. Valenzuela
由于其低频谱衰减率，传统的正交频分调制（OFDM）不适合支持异步接入、用户特定的子载波间隔和符号周期以及频谱聚合，所有这些都被设想用于第五代（5G）蜂窝网络。这激发了最近为5G设计新的多载波波形的工作。在本文中，一个统一的OFDM信号模型，其中包括变量采用循环前缀（CP）或零后缀（ZP）的保护间隔技术，无论是加窗或滤波，以增加传输信号的频谱衰减率;基于加窗和基于滤波的接收机也被容纳。给出了避免符号间和符号内干扰的信道冲激响应和任何加窗/滤波的充分条件。数值结果表明，在异步操作的多用户系统中，与用户特定的子载波间隔和符号周期，滤波和加窗产生大量的和可比的速率增益时，在发送器和接收器实现的标准OFDM;这些增益可以在相对于标准OFDM没有性能降级的情况下实现当系统同步操作并且所有用户具有相同的子载波间隔和符号周期时，系统可以被配置为（在通常感兴趣的SNR处）使用相同的符号周期。此外，CP-OFDM和ZP-OFDM具有几乎相同的速率对SNR性能。
Owing to its low spectral decay rate, conventional orthogonal frequency-division modulation (OFDM) is unsuitable for supporting asynchronous access, user-specific subcarrier spacing and symbol period, and spectrum aggregation, all of which are envisioned for fifth-generation (5G) cellular networks. This has spurred recent work on designing new multi-carrier waveforms for 5G. In this paper, a unified signal model for OFDM is presented, which encompasses variants employing either a cyclic prefix (CP) or a zero postfix (ZP) as the guard interval technique, and either windowing or filtering to increase the spectral decay rate of the transmitted signal; both windowing-based and filtering-based receivers are also accommodated. Sufficient conditions on the channel impulse response and any windowing/filtering are given for the avoidance of inter-symbol and intra-symbol interference. Numerical results are then presented to show that, in a multiuser system operating asynchronously and with user-specific subcarrier spacing and symbol period, filtering and windowing yield substantial and comparable rate gains over standard OFDM when implemented at both transmitter and receiver; these gains can be realized with no performance degradation relative to standard OFDM (at SNRs typically of interest) when the system operates synchronously and all users have identical subcarrier spacing and symbol period. Further, CP-OFDM and ZP-OFDM have near-identical rate-versus-SNR performance.