1. What is happening with the backhaul?
Numerous statistics and forecasts at Internet show that the use of data services on the mobile phone is growing up very fast. Several factors have helped this growing:
- The increase of smartphones sales in the last 3 years.
- The better performance of 3G-3’5G in comparison with GPRS in terms of download & upload speed.
- The user trends toward web 2.0 and social networks: Facebook, Twitter, FlickR and others have generated the demand of “Internet everywhere” in the users.
Increment of users with data plans
The increase in the number of data traffic users is good news for the telecom carriers, more users mean more money, but this increase also brings them three problems:
- More users mean more data traffic to handle, so carriers need more bandwidth. They have to upgrade their networks: in the access and in the backhaul.
- New services usually require more bandwidth. Web surfing is not sufficient. Telecom operators are facing a big challenge: Users want to watch videos on demand (YouTube, Vimeo…), talk with VoIP services (Skype), listen to real time music (Spootify), etc.
- The ARPU (Average Revenue Per User) seems to be decreasing in the present scenario.
These three facts (and some other ones) start to be a problem to theperformance and to the value of the 3G nets, which are not prepared for such a huge demand of data.
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There are several examples in the Web about bottlenecks in the 3G nets due the above factors: The problem of AT&T with the Iphone is one of the famous (LINK1).
The first step of AT&T has been to improve its towers and its backhaul (with new T-1 lines and DS-3 optical connections). But it is only a temporal solution; the increasing data demand has just started! Telecom carriers are worried about the impact of the incoming devices (new smart-phones and future devices like iPad) in its net.
New paradigm for the telecom operators
And here is where 4G technologies have appeared: LTE and mobile WiMax can achieve high data speeds, enough to cover user demands in the next years. However. Once an operator has chosen between LTE and WiMax (see article about this), another question is revealed: What about the backhaul?
If operators offer more bandwidth to users in the access, they need to improve the bandwidth of its backhaul in the same way. The present backhaul is not prepared to handle LTE/WiMax users…So, what are the requirements for the 4G backhaul? Lets see some of them.
2. Requirements of the new 4G Backhaul
2.1 Must support present networks: 2G, 3G and future networks (LTE)
The new backhaul model must protect the investment already done in 2G and 3G networks and must support the features of such infrastructures: roaming, handover and other techniques.
Furthermore, this new backhaul has to be prepared for the 4G evolution and the next generations. In this way, the huge amount of money invested will be amortized during several years.
The change toward an Ethernet based backhaul is increasing among carriers. Operators are looking for a cost effective technology, with high speeds and with the capacity of interconnection with the present equipment, which could set an all-IP scenario. LTE will boost this change in favor of an Ethernet based backhaul in the short term.
2.2 High speed in upload and download links
With 4G (with 3,9G also), users demand higher speeds of download and upload. New services like High Definition video on demand, High Quality photo sharing, mobile TV, etc, require a lot of bandwidth. To meet this huge demand for gigabytes, telecom operators need a backhaul solution suitable to provide a greater volume of data at lower prices than the current backhaul.
LTE and WiMax can achieve download speeds of 100Mb/s. The aggregate of N x 100Mb/s need a high capacity backhaul.
Download & Upload teorical speeds in Mbit/s
Customers will demand tons of Mb/s. A network, which pretends to be well prepared for 4G, will be required to manage very high bandwidths. At the present scenario, a backhaul based on TDM schemas can’t handle this requirement with a cost effective way. Ethernet equipments tend to have a better bandwidth/cost ratio than ATM equipments.
Moreover, one has to remember that it is not only the own traffic from the 3,9/4G network: one needs to take into account the aggregate traffic from the 2G and 3G networks too!
2.3 Low latency and QoS
Some new services in the 4G networks are extremely sensitive to latency. Voice calls over packet switched networks, online video games, video-conference, real time video-broadcast…All these services require low latency values.
The quality of the services depends a lot of the latency. And the quality of these services will be a key factor in the success of the networks: It is not only the cost of the services, it is also its quality and its performance what the customer will look for when 4G networks have arrived. For this reason, latency is a main factor here.
QoS deserves a lot of attention too. The tendency toward Ethernet changes from a circuit-switching network to a packet switching. With this change, the telecom operator must assure the QoS that a circuit-switching network can achieve in a packet switching scenario. In order to do this, operators are thinking in MPLS (again MPLS!).
QoS: Lower latency and SLAs
MPLS supports different QoS techniques. With this techniques carriers not only can obtain a good latency in the network, but they also can solve another problem: SLAs.
The SLAs (Service level agreements) of the carrier with other operators could require low latency too, so this parameter must be under consideration in the development of a new backhaul.
2.4 Multiprotocol and MPLS
The new backhaul must be very flexible and adaptive. The backhaul will mix different types of technologies: 2G TDM and 3G ATM, plus 4G Ethernet!
In this complex scenario, MPLS (“Multiprotocol Label Switching”) outstands. A network based on IP/MPLS can handle ATM & TDM packets. In this way, the protection of the 3G and 2G networks is assured while the next generation network is deployed at 100%. MPLS works in an Ethernet schema, so it fits perfectly.
Multiprotocol MPLS backhaul
2.5 Flexible: must allow SLAs and traffic from different operators
If the new backhaul is going to have a high capacity, it can transport traffic from different carriers. The owner can get benefits by selling bandwidth to other operators. This flexibility of the backhaul is an opportunity, but it is also a requirement: If the company already has a SLA with other telecommunications operators, the owner of the backhaul must maintain the service until the deal ends.
2.6 Increase ARPU. Decrease CAPEX and OPEX
The ARPU (Average Revenue Per User) is decreasing. The number of users has been incremented, but the revenue per bit is going down. A new business model based on the new services of the 4G-generation will be a key point to measure the success of the telecom operators in the next few years.
Moreover, operators need to find a better cost effective backhaul to improve their benefits. The reduction of CAPEX and OPEX is turning mandatory to compete in an increasingly difficult market.
2.7 Multiple synchronization for all protocols
In the new backhaul, there will be traffic from 2G/3G and from 4G (LTE). The new generation (4G) is clearly going to IP/Ethernet. This change affects the synchronization.
3G networks usually use the clock reference that travels through the E1-T1 to stay synchronized with the other elements of the network (they can use a GPS system also). But with the new schema of the network, the new Ethernet-backhaul will require additional methods to maintain the clock reference and the delay limits, based on the QoS engineering or on special physical layers to extract the clock from the data stream (Synchronous Ethernet).
3. Graphic summary
Requirements that the 4G-Backhaul must meet and have been discussed in this article:
Requirements of the 4G backhaul
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