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bạn có thể tiết kiệm rất nhiều thời gian trong giai đoạn thực hiện. Kế hoạch của bệnh viện để thêm hoặc xóa bất kỳ tòa nhà văn phòng là gì? Kế hoạch chính xác như thế nào? Thay đổi cấu trúc vật lý nên được xác định sớm để tiết kiệm thời gian và công sức. | Designing a Wireless Industrial Network Retail Case Study Chapter 7 253 also gives the clerk space so that he can actually go in the trucks while he checks the merchandise. Figure 7.7 Access Points on the First Floor and Warehouse The access points provide plenty of coverage for the predicted user density. Remember that these figures represent only a two-dimensional representation of the pattern the RF pattern actually covers a threedimensional range. Coverage for both floors is represented more accurately in Figure 7.8.This figure shows the RF pattern for the first floor overlaid with the RF pattern of the second floor. The RF pattern shows that almost all areas of the store are covered by at least three RF patterns. In fact most areas in the store are covered by five RF patterns. This extra coverage ensures coverage for the estimated user density. You have determined a total of four access points and six radios.To recap you plan one access point and two radios on the second floor one access point and one radio in the warehouse and two access points and three radios on the first floor.This plan allows for the future expansion of two radios. www.syngress.com 254 Chapter 7 Designing a Wireless Industrial Network Retail Case Study Figure 7.8 The RF Pattern Overlay for Both Floors Determining the RF Channel Optimization Since the radios in the access points will be very close in proximity to each other it is very important that they all operate on different 802.11b frequency channels.The 802.11b specification provides 11 different frequency channels. It is also important that the channels that are chosen be as separate as possible from each other. In other words you cannot set one radio to channel 1 and the next one to channel 2. Most access point vendors recommend a three-channel spacing between useable channels however in certain cases it is possible to push that limit to a two-channel spacing. A three-channel spacing will allow for three usable channels. Since you
