Reduce OPEX and simplify operations by moving GSM point-to-point TDM backhaul circuits – optimized for voice – to all IP transport. It’s possible without adding base station hardware. Synchronization methods pioneered by Nokia Siemens Networks ensure the same voice quality.
WCDMA backhaul moves to all IP
Operators running WCDMA networks see data traffic increasing rapidly as their customers buy smartphones and take to Internet Apps. Packet networks offer the right architecture for data traffic, so operators are evolving their WCDMA backhaul to all IP.
Should GSM voice-optimized backhaul also move to all IP? Operators with WCDMA and GSM networks can keep GSM on TDM backhaul circuits or use a hybrid of packet and TDM. However, neither option is OPEX efficient.
The OPEX efficient option
Immediately available is a very efficient, fully integrated GSM packet backhaul where TDM frames are converted into a flow of packets. An Ethernet transport infrastructure then forwards the packets. At the other end, the packets are again assembled into TDM frames. This is called pseudowire emulation. The basic function of a pseudowire is to packetize and encapsulate TDM traffic before transmitting it over the packet network – TDM on the outside, packet on the inside. Three different pseudowire flavors have been specified but CESoPSN is the most suitable for GSM.
Pseudowire transmission can be more efficient than native TDM
Pseudowire emulation makes transmission more efficient for three reasons: Operators can build a fully packet based network which allows for overbooking so less equipment can handle more traffic.
A single network simplifies operations for all services.
Pseudowire even transports GSM services more efficiently then TDM circuits using thirty timeslots if, on average, only 27 or less timeslots are filled because CESoPSN does not transmit empty time slots which saves bandwidth in packet networks.
Pseudowire works without additional base station hardware
CESoPSN is integrated in the Flexi Base Station and the Flexi Base Station Controllers, so the solution does not require additional hardware and GSM traffic can be carried over Ethernet from any GSM BTS to any other GSM BTS, including a mix of Ethernet and TDM links.
As a next step, packet Abis allows traffic optimization
Native packet Abis is available with RG20 and is the most efficient solution. It can be introduced without hardware changes in the Flexi Base Station in an Ethernet transport infrastructure based on CESoPSN. Where required, packet Abis can also be introduced in a TDM transport infrastructure using the Multi-Link Point-to-Point protocol to transmit IP packets over TDM. This allows for a fast rollout in the network.
Special use case: GSM and WCDMA colocated base stations with common all-IP backhaul
As an efficient site solution, it will be possible to backhaul GSM traffic via a colocated WCDMA base station using CESoPSN. CESoPSN comes with the WCDMA Flexi transport modules (FTIB, FTFB, FTLB) as a late feature in RU20.
Good voice quality needs reliable synchronization
Synchronization helps a receiver to find the beginning and end of each data unit within a continuous stream of ones and zeros. Without synchronization, voice handovers fail. TDM or hybrid transport provide excellent sychronization through the TDM frames. In an all-IP network, new synchronization solutions like IEEE 1588 v2 or Synchronous Ethernet are needed.
The NSN solution stands out
NSN currently leads the market in all-IP radio transport with over one hundred customers because we were first to develop and implement a reliable, cost-effective synchronization solution for all-IP backhaul, IEEE 1588 v2, which is also the first standards based solution.
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