Sub-Channelisation

List

Subchannelisation restricts the number of tones that are used in the uplink channel by the SS. This allows each tone to be transmitted at a higher power, allowing a subscriber station that may otherwise be out of range to obtain a link. It also creates a better balance between the uplink and downlink  transmitted power. The tones are grouped and unused tone groups may be allocated to other SSs. Data throughput for a single SS will be less as a result of sub-channelisation but the overall capacity of the link will not be affected.   

Subchannelisation selection is determined by the BS TRx dependent on the current transmit level requirements of individual SS's.   Not all SS may be capable of sub-channelisation (Airspan SS's are capable of sub-channelisation).  Once admitted to the system, uplink  modulation and sub-channel width are adapted, depending on uplink CINR reports and system configuration. In theory uplink sub-channelisation should provide a 3dB link budget gain for each halving of sub-channel width up to a maximum of 12dB.  And although the theoretical value is almost achieved with BPSK, the efficiency is less as the modulation rate increases.

The preference is  to use a 'prefer full bandwidth' scheme so as uplink CINR degrades, the SS uplink switches to lower order modulation while maintaining full bandwidth transmission.  When the uplink modulation reaches BPSK 1/2, and CINR degrades further, then subchannelisation is invoked to effect additional uplink gain. At present 'prefer full bandwidth' is the only management scheme that can be configured because other schemes such as 'prefer subchannelisation' (where decreasing modulation causes subchannelisation to be imposed first, and then only when 1/16th bandwidth is reached is more robust modulation selected) require the abaility to enter negative values for the burst profile thresholds, and this is not currently supported by Netspan. Burst Profiles Packages OFDM Channel Configuration Profiles

Add BS TRx Subchannelisation

Select the allowable sub-channelisation bandwidth by checking the appropriate boxes to align with the network strategy. It may be decided for example to allow only Full and one sixteenth to ensure that both channelised SSs and non channelised SSs are catered for, or all levels of subchannelisation may be set.  

• Mandatory Exit Threshold: Sets the level at which the channelisation will exit to the next level

• Mandatory Entry Threshold:  Sets the level at which the channelisation will enter from the previous level.

The following values will give a realistic example of the thresholds that should be configured in order to implement a 'prefer full bandwidth' scheme of bandwidth management.  This is the scheme where decreasing SNR causes a change to increasingly robust modulation types, until BPSK is reached; and then to begin to impose increasingly narrow bandwidth subchannelisation until 1/16th bandwidth is reached. At present, this is the only management scheme that can be configured because other schemes such as 'prefer subchannelisation' (where decreasing modulation causes subchannelisation to be imposed first, and then only when 1/16th bandwidth is reached is more robust modulation selected) is not (yet)supported.

The sample threshold values are:

BURST PROFILES:

SUBCHANNELISATION:

Note: MicroMAX only supports 'Full' sub channelisation.

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