The Mobile Market is experiencing solid growth in emerging countries. As an illustration, GSMA predicts the number of connections in Africa to jump from 620 Million in 2012 to 900 Million in 2015. Fierce competition between mobile operators as well as government and NGO initiatives encourage the development of mobile networks in underserved areas. In order to connect users in rural areas where basic telecommunication infrastructure is missing, mobile operators are relying on satellite communication to backhaul their GSM base stations.
Cell & Sat developed a Local Switching function optimizing local communications on the link between BTS and BSC that improves the end-user experience as well as reduces the amount of bandwidth on the satellite link. Local Switching is performed at the interface with the BTS. During a conversation between two mobile devices connected to the same satellite terminal, only signaling is sent to the GSM network while the voice traffic is looped locally. On the BSC side, silent frames are generated and transmitted together with signaling in order to insure full transparency with the GSM network. The solution is compatible with all GSM networks.
Satellite Bandwidth Savings
The Local Switching solution (LS) reduces significantly the bandwidth utilization on the satellite segment. It complements Abis bandwidth optimization equipment implemented on the Abis interface between the BTS and BSC.
In order to appreciate the potential savings obtained by the Local Switching function, we will first analyze the required level of bandwidth for different rate of local calls without the implementation of LS.
The communication between a user A and user B backhauled through the same VSAT terminal will go through the satellite link once to reach the mobile switching center (MSC) where the call is routed then a second time through the satellite back to the second user. A local call therefore uses twice as much bandwidth as normal communication between distant users which traverse the satellite link once.
For example for 20% of local calls i.e 80% of long distance communications, the percentage of bandwidth used for local call represents 33%.
The above figure shows that a significant rate of local calls can have a big impact on the cost of satellite bandwidth.
The Local Switching solution can bring substantial savings on satellite cost as voice traffic for local calls is routed locally off-loading the satellite resource.
In the following illustration, the satellite savings is calculated on a concrete case:
- Number of sites: 50
- Number of TRX per site: 6
- Signaling overhead: 10%
- Satellite cost (MHz/month): $ 3000
- Local calls rate: 20%
- Modulation 16QAM, FEC 7/8
In this scenario, the annual cost of satellite bandwidth is $ 1,512,000 without optimization.
After Abis optimization and Local switching the cost is lowered to $635,040, i.e. 58% savings.
The local Switching function alone brings an additional 30% savings on top of Abis optimization.
Bandwidth savings on the satellite link could as well compensate the increase of traffic due to data services whatever the type of GSM network: GPRS, Edge, 3G or LTE.
Mobile Backhaul Savings Calculator
The bandwidth simulator allowing you to calculate potential savings based on your own environment is accessible on Cell & Sat’s website, or by clicking the calculator image below.
Share post with friends