In this paper, a new hybrid methodology that combines precoding transform and companding transforms is being proposed for next-generation heterogeneous wireless networks. This method will improve the performance of the orthogonal frequency division multiplexing (OFDM) system by reducing the Peak to average power ratio (PAPR). A hybrid methodology that combines exponential companding (EC), which is a non-linear companding technique with Discrete Hartley Transform (DHT), as well as Walsh Hadamard Transform (WHT), is proposed and investigated. When the three simulated results are compared with original OFDM signal, piecewise linear companding shows an improvement factor of 28.8% over the original OFDM signal. Exponential companding is having an improvement factor of 33.49% over the original OFDM signal. Walsh Hadamard transform combined with exponential companding shows an improvement factor of 34.99% over OFDM. Discrete Hartley Transform combined with Exponential Companding is having an improvement factor of 38.09% over OFDM. The two proposed methods do not introduce any In-band distortion as well as Out-of-band Radiation when compared to the existing technique PLC (Meixia et al. in IEEE Trans Broadcast 60(3):532-539, 2014) which can be observed from the PSD analysis. Among the two proposed methods, the DHT precoded OFDM with the EC system shows significant BER improvement over the remaining methods. In addition to AWGN Channel, this proposed method shows significant BER performance improvement under the SUI-1 to 6 (WiMAX Channels) channels making use of 256-QAM as the modulation technique. As we move to a higher-order constellation, it is possible to transmit more bits per symbol; in such cases, the proposed technique will achieve better improvement in the performance of BER over all the existing techniques.

在本文中，正在为下一代异构无线网络提出一种结合预编码变换和压扩变换的新混合方法。该方法将通过降低峰均功率比 (PAPR) 来提高正交频分复用 (OFDM) 系统的性能。提出并研究了一种将指数压扩 (EC)（一种非线性压扩技术与离散哈特利变换 (DHT) 以及 Walsh Hadamard 变换 (WHT)）相结合的混合方法。当三个模拟结果与原始OFDM信号进行比较时，分段线性压扩比原始OFDM信号提高了28.8%。指数压扩比原始 OFDM 信号具有 33.49% 的改进因子。Walsh Hadamard 变换结合指数压扩显示比 OFDM 提高了 34.99%。与指数压扩相结合的离散哈特利变换与 OFDM 相比具有 38.09% 的改进因子。与现有技术 PLC（Meixia et al. in IEEE Trans Broadcast 60(3):532-539, 2014）相比，这两种提出的方​​法不会引入任何带内失真和带外辐射，它可以从 PSD 分析中可以看出。在提出的两种方法中，带有 EC 系统的 DHT 预编码 OFDM 显示出比其余方法显着的 BER 改进。除了 AWGN 信道之外，该提议的方法在使用 256-QAM 作为调制技术的 SUI-1 到 6（WiMAX 信道）信道下显示出显着的 BER 性能改进。当我们移动到更高阶的星座时，每个符号可以传输更多位；在这种情况下，与所有现有技术相比，所提出的技术将在 BER 性能方面实现更好的改进。