Specifications

General 15
The MIMO features require more than one radio channel and antennas, which will consume more
power and hardware space in the handset. Double sized channel (40MHz) support reduces the
amount of channels to half which makes channel planning much more difficult. Using short guide
interval (SGI) makes a client more sensitive to interference and may not benefit a moveable client
like a handset.
Using 802.11n mixed mode frame when transmitting creates larger overhead (double headers)
than if using legacy mode.
The following table lists some 802.11n features in the handset:
NOTE: The handset supports, but does not make use of, 40 MHz channel bonding. The handset
will prefer the use of legacy data rates in the uplink direction since the MCS rates introduce more
overhead.
The amount of channels that can be used for 2.4 and 5GHz bands is illustrated in the table in the
section
Section , “Basic Cell Planning”, on page -19.
Battery Considerations
Speech Time and Standby Time
Both the speech time and the standby time is greatly affected by the configuration of the network
and the power save mode used.
The standby time can be increased several times by following the instructions in chapter Section
, “Beacon Period”, on page -28 and Section , “DTIM Interval”, on page -28.
During a call, the power savings are significant with the handset in U-APSD mode compared to
Active mode. Note that given times are approximate since there are numerous of variables that
affect both the speech and standby time. If the network supports U-APSD, it is strongly recom
-
mended to use it.
NOTE: If U-APSD is unsupported by the infrastructure, the handsets will use Active mode even if
they are configured to use U-APSD.
If U-APSD is unsupported by the infrastructure, consider the following regarding PS-Poll and Ac-
tive mode: PS-Poll mode consumes less power than Active mode and thereby extends the speech
time. However, PS-Poll mode is designed for low-density residential installations with a single user
per AP and cannot meet high speech quality requirements. Therefore, PS-Poll mode is not recom
-
mended for use when high speech quality is required; in this case, Active mode is a better choice.
802.11n feature Supported Comment
Greenfield mode N Greenfield mode is unsupported.
40 MHz channel
bonding
N Channel bonding is used to increase bandwidth and a VoWiFi
client will not gain much with these higher rates. The handset
will not use 40
MHz channels but can operate in that environ-
ment if allowed by the system. Battery lifetime is also negatively
affected if using 40MHz channel width instead of 20MHz chan
-
nel width.
SGI N Using Short Guard Interval (SGI) increases the probability for
transmission errors and is therefore not applied by the handset.
MIMO N The handset uses SISO because it does not need to communi-
cate with higher bandwidth and to extend battery lifetime.
Block ACK Y Block ACK is supported but not always beneficial to use for Vo-
WiFi.