Ngoài ra, tương thích ngược với 802,11, có nghĩa là không thiết bị đầu cuối có thể nhận được các dòng ứng dụng QoS cho phép. Chương này mô tả các biện pháp nhằm cải thiện QoS 802,11 mạng với mục tiêu giảm độ trễ, jitter, mất gói tin, | Objections Due to Interference and QoS on Wireless Networks 153 Conclusion The specification is based on more than a decade of experience in design of WLAN protocols and was built from the ground up for real-world wireless conditions. Also is backward compatible with that is terminals can receive QoS-enabled application streams. This chapter described measures aimed at improving QoS in networks with the goal of reducing latency jitter and packet loss which detract from good voice quality. These wireless networks are potentially capable of delivering QoS and voice quality comparable to the PSTN. Note that the RBOCs were losing phone lines to cell phone service providers at an alarming rate for the RBOCs during 2002. In fact the RBOCs have recorded percentage-wise their first decline in lines in use since the Great Depression. Cell phone service is admittedly inferior in quality to that of the PSTN yet given the trade-off in mobility consumers are accepting a cell phone delivering inferior voice quality over a land line from the PSTN. The motivating factor for land-line customers to drop their service from the RBOC is the convenience in mobility offered by the cell phone as well as certain price advantages free long distance in off-peak hours . The point here is that ultimately the QoS of the PSTN is not an absolute requirement for consumers. The PSTN is doomed if it must compete with in that using potentially delivers at least comparable QoS in both voice and data services while offering data rates up to 11 Mbps compared with most DSL plans at 256 Kbps . Given that consumers will trade QoS for convenience and price as witnessed by the loss of lines to cell phone service providers it is not hard to imagine they would trade off the PSTN for the convenience of greater bandwidth and the wider range of services video on demand videoconferencing and so on available with that greater bandwidth. .
