Telecom

Providing high traffic capacity while reducing network costs Vinjett
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High-speed mobile backhaul demonstrators
The transition to new mobile technologies calls for an increase in backhaul capacity. The initial rollout of LTE will require a capacity of 100–150Mbps. Future releases will increase this requirement to gigabits per second all the way to the cell site.
Jona s H a n s ry d p e r-er i K e r i K s s on

With increasing demand for highcapacity mobile data services and a simultaneous decline in revenue per bit, network operators face the challenge of providing high traffic capacity while reducing overall network costs. At the same time, profitable migration needs the availability of high-capacity backhaul solutions. This article presents two highspeed technologydemonstrators: one for microwave, a singlecarrier GbE microwave link; and one for copper, a 500Mbps vectorized VDSL2 link.
The mobile backhaul network provides connectivity between the radio base station (RBS) site and the switch site at the edge of a transport network. Ericsson divides the backhaul architecture into two distinct parts (Figure 1) with separate requirements1 :

the low radio access network(LRAN) and the high radio access network (HRAN). The HRAN typically aggregates traffic from several LRAN networks using an existing fiber or microwave network, such as a metro network. The LRAN, which is frequently microwave-based, provides the last mile of connectivity for the RBS sites. The LRAN typically aggregates traffic from 10 to 100 RBS sites and feeds it into the HRAN. Owing to the largenumber of cell base station sites in the LRAN and the dynamic changes in the network, the LRAN must be cost-effective, simple, upgradeable, flexible, and able to provide peak capacity. Globally, LRANs use multiple physical link technologies (microwave, copper, and fiber), depending on operator strategy and availability at the site.2–3 Microwave usually provides the lowest total cost of ownershipwhen no other infrastructure is available at the cell site, and it is today the dominating LRAN backhaul technology. However, both fiber and copper serve as common first-mile backhaul solutions in many parts of the world.

Why we need high-capacity backhaul Mobile broadband has been a huge success thanks to the launch of flat-rate high-speed packet access (HSPA) services, which triggered asharply rising demand for mobile data services. It is anticipated that this trend will continue with the rollout of HSPA Evolution and 3GPP Long Term Evolution (LTE), which reduce the cost per transported bit. Historically, the transition to new mobile technologies has resulted in the need for a fourfold to fivefold increase in backhaul capacity. With the rollout of LTE, this translates into an LRANbackhaul capacity of 100–150Mbps. And future releases of LTE will increase the requirement for backhaul capacity to gigabits per second (Gbps) all the way to the cell site. Fiber access is the obvious first choice of technology for any high-speed link. The capacities of point-to-point or gigabit passive optical network (GPON) links exceed any LTE backhaul requirement so far.4 However, microwave andcopper also provide technologies for reaching Gbps capacity. High-capacity microwave links The conventional spectrum for microwave backhaul offers frequency bands between 6GHz and 38GHz. Each band is split into several narrow-frequency channels to ensure that the available spectrum is used most efficiently. The widest channel offers approximately 50MHz of bandwidth. Using advanced modulationformats, these bands support up to 500Mbps on a single carrier. Polarization multiplexing and multiple-input/multiple-output (MIMO) techniques may further increase spectral efficiency. Likewise, adding

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Terms and abbreviations
3rd Generation Partnership Project access gateway American wire gauge base station controller customer premises equipment DSL access multiplexer far-end crosstalk...