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由于无线信道的时变性、频率选择性、加性噪声以及发送和接收端晶体振荡器频率非一致性的影响, 实际的 OFDM 系统中总存在时间和频率同步误差定义了归一化干扰功率(NIP)来研究这两种误差对系统性能的影响. 在此基础上我们首先推导出: (1) 由时间误差产生的 NIP 公式和它的两个上界; (2) 由频率同步误差产生的 NIP 公式和它的两个上界, 这两个界比 Moose 上界更逼近实际 NI值. 然后, 通过在典型短波和中波信道的仿真进一步验证了这些界的有效性和正确性. 这些界有助于通信工程师在实际应用中在给定 NIP值的条件下选择满足系统要求的时间和频率同步算法. 同时, 还提出一种新的方法以减少OFDM系统对时间同步算法的精度要求, 该算法能实现时间同步精度和频谱利用率的有效平衡.
Due to the time-varying wireless channel, frequency selectivity, additive noise and frequency non-uniformity of the transmit and receive crystal oscillators, the actual existence of time and frequency synchronization errors in an OFDM system defines the normalized interference power (NIP ) To study the impact of these two errors on system performance. Based on this, we first derive: (1) the NIP formula resulting from the time error and its two upper bounds; (2) the NIP resulting from the frequency synchronization error Formula and its two upper bounds, the two bounds are closer to the actual NI value than the upper bound of Moose. Then the validity and correctness of these bounds are further verified by simulations on typical short and medium-wave channels. Which can help communication engineers select the time and frequency synchronization algorithm that meets the system requirements under the given NIP value in practical application.At the same time, a new method is proposed to reduce the precision requirement of the OFDM system to the time synchronization algorithm, It is possible to achieve an effective balance of time synchronization accuracy and spectrum utilization.