- 學位論文
結合網路編碼與階層式調變提昇機器對機器之通訊效能
Utilizing network coding and hierarchical modulation for enhancing M2M communication performance
摘要
隨著室內環境下使用行動通訊裝置的人數快速增加，改善室內環境訊號不佳的問題更是刻不容緩，在室內環境當中，一般家庭中大多的裝置都是低功率且價格低廉的裝置所以資源受到限制，因此部分的室內裝置可能因為距離毫微微型蜂巢式基地台(Femtocell)太遠或者是通道環境不佳，造成傳輸資料位元的錯誤率大幅上升，所以可能會導致部分裝置無法進行資料傳送。 本論文研究是將網路編碼與階層式調變(Hierarchical Modulation)結合，因為在一般的網路編碼中，接收端需要由已知的訊息來解開網路編碼，造成傳送端需要多傳一次已知的訊息來讓接收端解編碼，但經過階層式調變，傳送端可透過階層式調變的方式來傳送，進而減少一次的傳送。本論文使用"XOR軟式解碼"方法，經過Iteration來使錯誤率降低。 本論文以s1、s2與s3三個為一組的機器對機器之傳輸機制，透過結合網路編碼與階層式調變，且經由本論文的挑選機制來進行傳送，首先將s1的通道設定在較差的狀況，通道的SNR僅有6dB左右，而在s2設定的SNR必須高於s1 3dB以上，並將s3設定與毫微微型蜂巢式基地台距離最近，因此通道SNR為10dB~15dB左右，透過本論文的機器對機器的傳送機制，三者的位元錯誤率(BER)都可以降到10^-4以下，然而在吞吐量(Throughput)方面，雖然將犧牲一些s3的吞吐量，但是在s1的吞吐量方面能獲得3倍以上的效能，並且在s2也能有2.9%的吞吐量的上升，然而在整體的吞吐量方面，仍然有一定的提升。
並列摘要
In nowadays, the number of people using mobile devices in indoor environment is fast increased. To improve the poor transmission quality in the indoor environment is getting more and more urgent. For the devices using in indoor environment, the resources are always limited because of the low power and less capability. The bit error rate will substantially rise because the distance between the devices and the Femtocell is too far or the transmission environment is awful. Thus the machine may not be able to transmit data correctly. In this thesis the combination of network coding and hierarchical modulation schemes is proposed to improve the performance of indoor machine-to-machine communications. For network coding scheme, the receiver should have the known information to decode the signals, so the transmitter should send the known information additionally. But if we combine the hierarchical modulation, the data of machines can be modulated in a hierarchical form for transmission. It could avoid the additionally transmission. Besides, the “XOR soft decoding” and iteration method are used to decode the data which will reduce the BER. In this thesis, we consider three machines as a group. The machine, s1, is in a bad conditions, says SNR is only 6dB. The SNR of machine s2 is 3dB higher than machine s1. However, the machine, s3, is in a good transmission condition which has SNR in 10~15dB level. By applying the proposed method, the bit error rate of the machines s1, s2, and s3 can be improved. Though the throughput of machine s3 will be sacrificed a little bit, the throughput of machine s1 will increase more than three times. Besides, the machine s2 can reach 2.9% improvement in throughput.