无线网络教学资料r-ch3--pd思科无线网络设计--sitesurveybaseap

1、无线网络设计及部署,模块内容,部署方法 部署需求 Protocol Comparison 企业无线网 Coverage & capacity 确定AP数量和位置 Z factor design Site Survey 验证无线网部署,Determine Deployment Requirements,Assess,Determine AP Count & Placement,Deploy,Place Access Points,Survey WLAN,Verify,Planning Tools,Site Survey,Z Factor,部署方法,Protocol requirements 80

2、2.11b/g 802.11a Client devices WNIC PDA Phone Client density Typical Peak Expected throughput 802.11b is typically 2 Mbps 802.11g is typically 11-14 Mbps 802.11g is typically 2-4 Mbps with 802.11b clients presents 802.11a is typically 11-14 Mbps,部署需求容量考虑,协议比较,The standards that must be supported by

3、an enterprise WLAN are usually dictated by the devices that require support. Currently 802.11b clients are predominant but what is right answer for your enterprise WLAN solution? 802.11b Pro: Highest market penetration Con: More interference & noise may be found in the 2.4GHz band Con: Only provides

4、 3 non-overlapping channels Con: Can suffer from multipath issues Con: Client driver quality (consumer versus enterprise) 802.11g Pro: Higher throughput Pro: OFDM technology reduces multipath issues Con: More interference & noise may be found in the 2.4GHz band Con: Only provides 3 non-overlapping c

5、hannels Con: Throughput degraded in the presence of 802.11b clients 802.11a Pro: Higher throughput Pro: OFDM technology reduces multipath issues Pro: Provides FCC 24 non-overlapping channels Con: Lower market penetration 802.11n Pro: MIMO/Channel combined/Packet Aggregation provide More Stable conne

6、ction, higher performance and longer distance Con: Not finalized yet Con: Need more power,Coverage Areas Full or partial Coverage Hole Goal 0% - 10% (Typically 2% 5%) Building Construction Type Typical Offices (cubes and walled offices) Walled Offices (drywall office only) Walled Offices (brick and

7、concrete walled offices) Other (example arenas, stock exchange, convention center, large warehouse) Building Characteristics Homogeneous same construction type throughout Cubes and walled offices throughout and/or floor to floor Heterogeneous mixed construction types Drywall office area with shippin

8、g warehouse in back,部署需求覆盖,部署需求障碍物考虑,Normal construction provides a myriad of wireless obstacles,Distant corners,Walled office area,Break room with microwave,Concrete walls with iron rebar,High mounting positions,Meeting room with high peak users,Elevator shaft and stair wells,部署需求提问,How many access

9、 points do I need? Purchase more AP than determined AP count At best case, will allow over-deployment to ensure seamless coverage and higher capacity allowing Cisco Airespace controller to compensate for overlap At worst case, will cover unforeseen coverage hole Where should I place the access point

10、s? Place AP where WLAN clients will be located Do place AP in a meeting room as opposed to an adjacent hallway Do place AP in a central location which can cover several walled offices Do not place APs in a wiring closet Place AP in the middle of coverage areas How many controllers will I need? Provi

11、de enough controllers to perform the suggested high availability schemes available to provide enterprise reliability Where should I place the controllers? Place the controllers in different wiring closet to reduce power loss issues,部署需求AP摆放,Over cubicles outside of offices,In meeting room with high

12、peak users,Inside load bearing walls,Positioned to cover 2 rooms with non-load bearing walls,企业无线网覆盖和容量,80 ft,Basic coverage, low cost,Enterprise coverage & capacity,60 ft,802.11a:11-14 Mbps 802.11g:11-14 Mbps 802.11b/g:2 / 2-4 Mbps 802.11b:2 Mbps,Graphic is using only 3 channels for interference av

13、oidance,企业无线网策略,Smaller, overlapping cells Increased average capacity 802.11a can provide more channels to reduce interference Provides higher availability in the event of an AP failure APs should not be placed too close together since clients will still transmit at normal power output Clients can c

14、ause interference issues with other APS and clients,Enterprise coverage & capacity,60 ft,802.11a:11-14 Mbps 802.11g:11-14 Mbps 802.11b/g:2 / 2-4 Mbps 802.11b:2 Mbps,Graphic is using only 3 channels to show option to avoid interference,确定AP数量和位置Z Factor,Z factor allows conversion of an AP coverage ar

15、ea to square footage Together with the building type and average desired user performance, the Z factor calculation can quickly estimate the number of required APs,Increased signal strength means greater throughput limited by signal standard 802.11a will have increased throughput over a wider range

16、than 802.11b,Z FactorPremise,Average Signal,Z FactorBuilding Reference,Z FactorAP 数量,Next define the coverage area for each floor in the building Divide into rectangles, then calculate APs needed by dividing the area of each rectangle by the Z factor squared,Example is for a typical office building

17、with a desired average user throughput of 5 Mbps,Due to the gain of an Cisco 1000 series AP, 10% more AP should be added from a given calculation,Z FactorAP 位置,Place the AP in the center of the coverage areas,Example is for omni directional antenna,Due to the gain of an Cisco 1000 series AP, AP shou

18、ld be staggered to accommodate coverage area shape,确定AP数量和位置Site Survey,More rigorous method to determine AP count and placement Z Factor calculation can be used to determine AP count while Site Survey can be used for actual AP placement Requires measurement of actual coverage areas to determine cor

19、rect placement,Site SurveyOverview,Cisco 1000 series APs are configured for site survey mode First AP is placed at a zero/zero coordinate and then the Ekahau Site Survey Tool is used to determine coverage boundary Then place AP on coverage boundary in the middle of the coverage area Then use Ekahau

20、Site Survey Tool to determine new coverage boundary Then place additional AP with RF coverage areas adjacent to placed AP Then use Ekahau Site Survey Tool again to determine additional coverage boundaries A single set of Cisco 1000 series APs can be moved to different locations on the building floor

21、 until all AP placement is defined Ekahau Site Survey tool should be used to verify the final AP placement and document the WLAN,Site SurveyCisco 1000 series AP Site Survey Mode,Requires opening of Cisco 1000 series AP and setting of internal jumper Requires powering of Cisco 1000 series AP In site

22、survey mode, the Cisco 1000 series AP is beacon only device and will not support data or monitoring services In site survey mode, the Cisco 1000 series AP Transmit power is 18 dBm for 802.11a on channel 52 Transmit power is 19 dBm for 802.11b on channel 11 In site survey mode, the Cisco 1000 series

23、AP power LED will flash green Site survey mode will not support external antenna Site survey mode is used exclusively for site surveys or troubleshooting,Site SurveyCisco 10 xx series AP Site Survey Mode (continued),You must first open the cover by removing the screws at the base of Side A with a T-

24、10 security Torx,Cisco 1000 series AP Site Survey Mode requires a physical configuration,Then you must open the cover and jumper the Site Survey pins 1 & 2,Site SurveyCisco 10 xx series AP Site Survey Mode (continued),Cisco 1000 series AP Site Survey Mode requires a power source,Site SurveyAP 数量和位置,

25、Place the AP at 0:0 coordinate of a coverage area (1). Perform a site survey to determine the signal strength of the coverage area. Mark where the rate falls to the minimum acceptable value until you have traced a semi-circular pattern on the floor which will determine the coverage boundary. Move th

26、e original AP to a centrally located position on the coverage boundary (2) to create the first coverage area.,Site SurveyAP 数量和位置 (continued),Perform a site survey to determine the signal strength of the new coverage area. Mark where the rate falls to the minimum acceptable value until you have traced a circular pattern on the floor which will determine the coverage bound