VAMOS Trial Test Live Network

Voice services over Adaptive Multi-user channels

on One Slot (VAMOS)

Scope and Objectives

What is VAMOS? When and Why to use ? How VAMOS Work? VAMOS limiting factors Huawei VAMOS Requirement KPI Result Conclusion

What is VAMOS

VAMOS is Voice Efficiency for GSM which with this technology you can have up to 4 calls per TS.

As VAMOS does not require new voice channels to be defined, it is an extension of the currently defined full and half rate channels.

Why and when to deploy

There are numbers of reasons to use VAMOS feature:-

Voice traffic growth .

Network with less frequency bandwidth.

Expand EDGE mobile broadband service . 3G/LTE Introducing Spectrum re-farming

VAMOS work principle

Transmitting-simultaneously sending 2 calls. - TRX: New modulation with double bit rate Adaptive QPSK

- MS: Still using GMSK – one call per MS . Receiving - separating 2 calls from each other . -TSC: Separating the two calls transmitted on the same timeslot .

-MS :SAIC filter out its call using TSC.

-TRX:SIC(IRC) filter out its call use the TSC.

VAMOS requires a pair of training sequences to be allocated to users in a VAMOS pair. These training sequences are the key when separating the paired users from each other. While the standardized VAMOS solution supports new training sequences optimized for new VAMOSmobiles, VAMOS can be used in networks with a significant penetration of SAIC mobiles, using the already defined set of legacy training sequences

VAMOS work principle

For the Mobiles side there are several functional level. > SAIC which already available in Market

> VAMOS I &II Near Future (3GPP Rel 9 Q1 2010 but commercial available 2103

and 2014 )

Due to VAMOS Power control less power required so that with legacy mobile can be paired in way extra power for legacy mobile granted due to low VAMOS mobile penetration

3GPP vs Huawei Network Capacity Gain Expectation

From 3GPP capacity gain simulation in early stages when the Mobiles support SAIC with 50% at least can have almost 40% gain but from Huawei trial experience with the same penetration the gain are from 10 to 22%

Limiting Factors

Coverage Two MS sharing one TS - 3dB less power for each MS AQPSK Modulation - Similar to EDGE peak to average ratio 3 dB reduced power

Limiting Factors

VAMOS Efficiency

From the above chart show that when ever the interference sources become higher the MS SAIC(VAMOS) efficiency become less

Huawei VAMOS Impact on equipment resources

1- The VAMOS feature is supported by the following radio frequency (RF) modules: GRFU V1, GRFU V2, GRFU V2a, RRU3008 V1, RRU3008 V2, RRU3928, RRU3929.

2- Maximum TRXs configured per cell are 4TRX VAMOS support.

3- Power Control VAMOS power control must be enabled together with the optimized Huawei power control and power control III. 4- Transmission resources After VAMOS is enabled, more transmission resources of the Abis, Ater, and A interfaces are required. Take E1 transmission as an example. If the existing E1 resources become insufficient after VAMOS is enabled, extra E1 resources are required on the Abis, Ater, and A interfaces.

5- Interface board resources After transmission resources are added, additional Abis, Ater, and A interface boards are required if the current interface boards are incapable of processing all the transmission resources.6- Voice processing resources After VAMOS is enabled, the network capacity for processing voice services increases. Additional speech service processing boards are required if the current speech service processing boards are incapable of processing all the voice services.

VAMOS KPI result

Impacts on KPIsVAMOS can expand network capacity and decrease congestion rate. However, it has adverse impactson network KPIs, especially speech quality, including receive quality, call drop rate, and mean opinion score (MOS). Therefore, it is recommended that the Half-Rate Service feature be preferentially enabled to expand network capacity and VAMOS be enabled only when network capacity needs to be further expanded. In addition, VAMOS is not recommended to be deployed for telecom operators who are very concerned about speech quality.

Total Erlang vs VAMOS Erlang

This graph shows that the Daily total traffic vs VAMOS total traffic from the launch of VAMOS till the trial

tests for parameters tuning.

HW Efficiency % & SAIC penetration(VAMOS MS)

This graph shows Hardware Efficiency( Saving network resources(Number of required TRXs)

SAIC penetration(VAMOS MS)

This graph shows mobile support SAIC(VAMOS I) This graph shows mobile support SAIC(VAMOS I) hourly as sometime the penetration touching 100%

TCH Drop rate vs DL/UL Quality 0 %

When Two call multiplex on one slot the user quality effected and probability of call drop increase with VAMOS feature this due to mobiles either support VAMOS or not.

TCH Congestion Rate,CSSR and HOSR

Whenever VAMOS activated the congestion in network reduced especially for loaded traffic network and such KPI like CSSR and HOSR can be kept if properly parameter sets for VAMOS on cells and other part of networks elements

Conclusion

According to test the settings in term of effective parameters make VAMOS traffic despite the Quality degradation are :-

Network must have high penetration for SAIC allowed .

Proper parameters sets as below are the most effective one. 1- Allow Multiplex for Unknown SAIC MS to be ON 2-

3-

Parameter ValueDL RX Qual Thres of Terminal Identify 10UL RX Qual Thres of Terminal Identify 10DL Rx Qual. Thres. of Established Calls 10 to 30UL Rx Qual. Thres. of Established Calls 10 to 30

UL RX Bad Qual. Demultiplex Thres. 30 to 50DL RX Bad Qual. Demultiplex Thres. 30 to 50

Parameter ValueChannel Multiplex Load Thres. 25 to 50

Load Thres. of Channel Demultiplex 0 to 25