混合式自動重傳請求(Hybrid Automatic Repeat reQuest，HARQ) 是一種結合了FEC與ARQ 方法的技術，由前一次錯誤封包中記錄下有用的資訊，提供之後的解碼使用。本論文以現行無線通訊蜂巢式系統為基礎，模擬了包含一般通道探討時必備的大範圍訊號衰減所造成的遮蔽衰落模型、路徑衰減模型，小範圍訊號衰減所造成的Rayleigh衰落。在自動回覆請求機制，以原始的Type I型配合AMC和新型的Type I型(Chase Combining)的HARQ為主，而最終重傳機制選擇的方式為根據模擬時系統規格的要求，例如重傳次數限制、重傳暫存器大小限制，PER(Packet Error Rate)小於10%等限制為我們選擇的要件。
正交分頻多工系統已成為無線通訊應用中最熱門的傳輸選擇，由於此技術擁有高速率的傳輸，在無線環境中，可以簡單並且有效的做傳送與接收，而為了能夠在接收端估計通道，在傳送端會配置領航訊號 ( Pilot signal )，利用傳送端以及接收端已知的領航訊號來估計通道的變異。本論文則利用領航位元作階層式調變，利用階層式調變後的領航位元的每一個階層之間位元錯誤率的不同來估計載波頻率飄移。
Hybrid automatic repeat request (HARQ), is a technique that combines the forward error (FEC) correction technique and the ARQ process. In this study we consider a basic cellular communication system and propose a complete system simulation model that it not only includes the common simulation model as discussed in the wireless communication system such as the shadowing fading due to large-scale attenuation, path-loss attenuation and small- scale Rayleigh fading etc. In this study we propose the system architecture for HARQ retransmission in a wireless communication system, two retransmission mechanisms are considered in the architecture, one is the combination of the conventional Type I retransmission with AMC and the other is the new Type I retransmission, Chase Combining. It depends on the system requirements and system specifications such as the maximum retransmission number allowed, the buffer size in the store of the retransmitted packets and packet error rate (PER) etc. to determine which retransmission mechanism will be exploited.
Due to the development and advancement of wireless communication, many technologies utilizing communication as their core technologies will not be restricted and confined in the wired line network systems. In the installations of wireless communication system, it has many advantages such as to reduce the terrain barrier, to conquer the communication distance restriction and to reduce the amount of cable installations. In Taiwan for its existing and ubiquitous installed monitoring systems, if in their future new systems installations, no matter they are for traffic, community or campus, and if they are installed with wireless monitoring networks then they will become the focal attentions in the convenience and its cost effectiveness with the wireless systems installations.
In this report we study the feasibility of the installation of wireless campus monitoring network through the field trials in the campuses of National Taiwan University and National Taiwan University of Sciences and Technology. We adopt the just in service WiMAX and the available HSDPA (3.5G), EDGE (2.5G) technologies to proceed in the system performance test when video, VoIP signals are simultaneously transmitted through the system by using Skype software. The transmission of HRV (Heart Rate Variation) through FTP format with these three systems is also studied. The resulting system performance and their characteristics of using WiMAX, HSPDA and EDGE in the transmission of video, VoIP and HRV are summarized and compared. With these test data and results it may provide some valuable reference data to the system designers and service providers when they are considering the installations of wireless surveillance system in the university campus.
Currently orthogonal frequency division multiplexing wireless communication systems have become the most popular application of transmission choice, because this technology has a transmission rate of speed in a wireless environment, you can make a simple and efficient transmission and reception, and be able to order at the receiving end estimated channel, the sender will be configured navigator signal (Pilot signal), the variance using the sender and the receiver side known navigator signals to estimate the channel. In this paper, the use of navigator bit as hierarchical modulation, bit error rates between not using hierarchical modulation after every bit of the same class navigator to estimate the carrier frequency drift.