The high availability of the new smartphones, like iPhone and the introduction of the new 3G technologies – like HSPA (High Speed Packet Access) – already deployed in many countries have led to an increasing demand for new bandwidth-hungry services such as web browsing and mobile video streaming. This demand is also fuelled by the emerging 4G technologies – such as EPS (Evolved Packet System) and WiMAX (Worldwide interoperability for Microwave Access) – which are now beginning to be implemented and are aimed at realising mobile broadband. The end-users can now receive peak rates up to 45Mbps with HSPA+ which are expected to reach up to 100Mbps DL in 4G.
These high data rates can be achieved by applying a number of changes to the radio interface, such as introducing MIMO, adaptive modulation and coding along with higher modulation schemes, new multiple access techniques (OFDMA), etc.
However the high rates achieved over air can be limited by the backhaul network and lead to severely degraded service provided to the end users or even signalling failures and dropped calls. This is due to the fact that most of the current backhaul networks are deployed using TDM/ATM techniques which are efficient for voice services but not optimal for the new data services. Thus a re-design of the backhaul needs to be considered by the operators in order to cope with the forthcoming backhaul bottleneck.
The straightforward solution is to increase the number of leased lines and microwave links in order to provide more bandwidth in the backhaul. However this approach is neither cost effective nor bandwidth efficient for such a dramatic increase. Furthermore the 4G technologies require an all-IP transport logic.
Thus operators have to start introducing packet switched technologies such as MPLS/IP in the current backhaul deployments in order to be able to support the new services advertised but also to make a step towards 4G upgrade.
This upgrade will probably happen in phases. As a first step towards IP backhaul the HSPA traffic can be offloaded over Ethernet transmission network, while the voice services can still be transmitted over traditional TDM/ATM networks and equipment already support this hybrid technology. Pseudowires (PWE3) can then be introduced to emulate circuit switched networks and allow the transmission of TDM/ATM over Ethernet.
Summarising, the new technologies and the supported services require a significant increase in the supported data rates, which is realised by improvements in the radio interface. This data rate increase is causing a bottleneck in the current backhaul deployments which are mainly designed for voice services and a subsequent re-design of the backhaul is also required in order to provide an efficient and cost effective solution for the operators. IP/Ethernet technologies are the way forward for the next generation of the backhaul networks being in the form of hybrid TDM/IP solution, circuit emulation, or native IP.
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