基於濾波器組多載波技術之新世代無線通訊毫米波基頻接收機設計

Abstract

為了滿足未來幾年的爆炸性無線通訊流量成長，新世代無線通訊將會利用毫米波頻段獲取更寬的頻譜進行破壞性創新技術來大幅增加資料傳輸量。此外，新波形於無線通訊系統上受到各方矚目。由於濾波器組多載波 (FBMC) 相比於傳統的正交分頻多工(OFDM)有更優異頻譜抑制特性，數個研究組織將FBMC視為一個極具潛力的新世代無線通訊候選規格之一。因此，本論文的主要目標是將毫米波頻段傳輸以及新波形進行結合，用以提供更高資料率且更高傳輸效益以符合新世代無線通訊傳輸之需求。

首先，在此論文中，我們提出應用於IEEE 802.11ad與IEEE 802.15.3c規格之下且具有單載波(SC) 和OFDM雙模式並能抵抗非直視(NLOS)和直視(LOS)通道的基頻接收機設計。為了滿足規格指定的2.64GHz的超高取樣率，此提出的基頻接收機具有八倍平行、前饋路徑且深度管線化的設計。為了節省硬體實作面積，雙模式共用和記憶體節省分別達到99%的共用率和減少51%的記憶體使用量。此雙模基頻接收機使用40奈米互補式金屬氧化物半導體通用製程進行硬體設計。量測的結果顯示，當此晶片工作在330/500MHz工作頻率時，可以提供高達 9.24/14 Gb/s實體層資料率。

接著，我們提出一個基於IEEE 802.11ad與IEEE 802.15.3c規格之FBMC基頻接收機設計方法用以改善OFDM傳輸效率不足以及旁辦抑制不佳的問題。在 FBMC模式中我們採用 PHYDYAS 組織所提出的濾波器係數來實現置入於傳送端和接收端的原型濾波器，我們亦提出一個具有新穎的記憶體存取重組架構之多項網路來實現原型濾波器。對於濾波器造成的本質干擾將會影響傳送端所置入的領航子載波，我們採用了輔助領航子載波以及提出數個領航子載波排列方法來克服此問題。

得利於FBMC優異的頻譜抑制效果，原保護頻帶可以被放置更多資料子載波以提高頻譜使用率。然而，此舉將造成邊緣資料子載波遭受較大的取樣頻率偏移，以及源自於同步階段中用以補償取樣頻率偏移的內插器造成頻域子載波的可變振幅衰減。所以，我們提出了一個基於內插的追蹤補償方法來解決此問題。另外，在FBMC中無循環字首抵禦多路徑效應，其造成的符元間干擾將破壞基頻系統之性能。對此我們提出了一個能抑制FBMC在長多路徑通道中遭遇到的符元間干擾與載波間干擾的最小均方誤差複合式反饋前饋等化器(MJFFE)。

最後，所提出之FBMC-OQAM整合進所提出的雙模式基頻基收機，達成一個具有SC/OFDM/FBMC的三模式基頻接收機。合成結果顯示，當此基收機採用 FBMC-OQAM模式並工作在500 MHz工作頻率時，SC、OFDM以及FBMC 模式分別可以提供7 Gb/s、14 Gb/s以及21.4 Gb/s的實體層資料率。更重要的是，與雙模式基頻接收機相比，所提出的三模式基頻接受機僅需多花費38% 面積的付出即能分別提升8.5%頻譜效益與41%頻寬效益。總共能提升53%的資料傳輸速度。

In order to meet the explosive growth of communication traffic in the coming years, one of the key technologies in the new-generation wireless communications is a disruptive move to millimeter wave spectrum with wider bandwidth for data transmission. Moreover, new waveform techniques are receiving particular attention in wireless communication systems. A number of research organizations regard the filter bank multi carrier (FBMC) as a strong 5G candidate because FBMC has the excellent spectral containment as compared with OFDM. Therefore, the main goal of this thesis is combining the mmWave band transmission and new waveforms for providing higher data rate and transmission efficiency to meet the requirement of new-generation wireless transmission.

First, in this thesis, we propose an 8X-parallelism SC/OFDM dual-mode baseband receiver for IEEE 802.11ad and IEEE 802.15.3c which can conquer the NLOS and LOS channels. For satisfying the 2.64 GHz specified in the standards, the proposed dual-mode baseband receiver is implemented with a deep pipelining, feed-forward and 8X-parallelism architecture. In order to reduce the cost of hardware implementation, the proposed dual-mode architecture unifies the algorithms used so that memory module sharing reaches 99% and reduces 51% memory usage, respectively. The dual-mode baseband receiver chip is designed with 40 nm CMOS GP process. The measurement results show the fabricated chip could operate at 330/500 MHz operating frequency, supporting the PHY data rate up to 9.24/14 Gb/s.

Then, we present a FBMC mode baseband receiver scheme based on IEEE 802.11ad and IEEE 802.15.3c to enhance the transmission efficiency and spectral containment in OFDM mode. In the FBMC mode, we adopt the filter coefficients proposed by PHYDYAS project to implement the prototype filters which are embedded into the transmitter and receiver sides. We also propose a novel memory access reordering polyphase network (PPN) architecture to realize the prototype filter. Also, the auxiliary pilot and pilot arrangements are also proposed to solve the problem that the intrinsic interference affect the inserted pilot subcarriers at the transmitter side.

Thanks to the excellent spectral containment of FBMC, the bandwidth efficiency could be increased a lot by inserting more data subcarriers on the guard-band subcarriers. However, this method will cause that band edge data subcarriers suffer more serious sampling clock offset (SCO), and varying amplitude distortion from the time domain interpolator, which is used to compensate the SCO effect in the synchronization stage. Thus, we propose an interpolation based method to solve this problem. In addition, the removal of cyclic prefix (CP) in FBMC causing the inter-symbol interference (ISI) and will destroy the performance of baseband system. In view of this, an MMSE joint feedback feed-forward equalizer (MJFFE) is proposed to deterministically suppress the ISI and inter-carrier interference (ICI) suffered by the FBMC in a long multipath channel.

Finally, the proposed FBMC-OQAM baseband receiver is integrated to the proposed dual-mode baseband receiver for realizing a SC/OFDM/FBMC triple-mode baseband receiver. According to the synthesis results, SC, OFDM and FBMC could support the PHY data rate up to 7 Gb/s, 14 Gb/s, 21.4 Gb/s respectively while operating at the clock rate of 500 MHz. Most importantly, FBMC mode as compared to the OFDM mode baseband receiver, only requires 38% area cost to pay the enhancements of 8.5% spectral efficiency and 41% bandwidth efficiency, respectively. In total, FBMC mode increases 53% data rate as compared to OFDM mode.