System Planning
Ascom VoWiFi System
TD 92408EN
9 December 2011 / Ver. G
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 Du
al 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 Wi
red 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 Hand
set
............................................................................ 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 Opti
mal Performance .................................................................... 25
8 Infrastructure Dependant Features........................................................................... 27
