Download ASCOM VoWiFi System Installation guide

System Planning
Ascom VoWiFi System
TD 92408EN
Contents
1 Introduction .................................................................................................................... 1
1.1 Abbreviations and Glossary................................................................................................... 1
2 General ............................................................................................................................ 4
2.1 Introduction to Wireless Planning ....................................................................................... 4
2.1.1 Adding Voice to a Wireless LAN ................................................................................. 4
2.2 Combination of Data and Voice Channel Assignments .................................................. 6
2.2.1 Legacy Network Not Using Any 802.11n APs ....................................................... 7
2.2.2 Customer Is Running Dual Radios a/b/g APs ......................................................... 7
2.2.3 Customer Is Adding 802.11n APs and Is Also Keeping Old APs ........................ 8
2.2.4 Customer Has Already Invested in 802.11n Dual Band APs and Has Replaced
All Old APs in the Same Position ................................................................................... 9
2.3 802.11 a-radio Support in the VoWiFi Handset............................................................ 10
2.4 802.11 n-radio Support in the VoWiFi Handset ........................................................... 11
2.5 Battery Considerations ........................................................................................................ 13
2.5.1 Speech Time and Standby Time .............................................................................. 13
2.5.2 Battery Lifetime........................................................................................................... 13
3 Wired LAN/Backbone Requirements.......................................................................... 14
3.1 Quality of Service (QoS) Recommendations .................................................................. 14
3.1.1 IEEE 802.11 Priority Field.......................................................................................... 14
3.1.2 IEEE 802.1q Priority Field .......................................................................................... 15
3.1.3 DiffServ, DSCP Value ................................................................................................... 15
3.2 End-to-End QoS...................................................................................................................... 15
3.2.1 Uplink, VoWiFi Handset to AP .................................................................................. 15
3.2.2 Downlink to Wired Network ..................................................................................... 15
3.2.3 Downlink, AP to VoWiFi Handset ............................................................................ 16
4 Security Considerations ............................................................................................... 17
5 Basic Cell Planning........................................................................................................ 18
5.1 Range vs. Transmission Rate.............................................................................................. 19
5.2 RF Signal Corruption in an VoWiFi System...................................................................... 20
5.2.1 Free Space Loss............................................................................................................ 20
5.2.2 Distance Attenuation ................................................................................................. 20
5.2.3 Multipath Propagation 802.11n Radios................................................................ 20
6 Co-Channel Interference .............................................................................................. 22
6.1 Clear Channel Assessment, CCA ......................................................................................... 22
6.2 Hidden Node Problem .......................................................................................................... 23
7 AP Placement for Optimal Performance .................................................................... 25
8 Infrastructure Dependant Features........................................................................... 27
9 December 2011 / Ver. G