4G LTE = 4th Generation Long Term Evolution

4G LTE Network.

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4G Network Architecture
OFDM - Othogonal frequency Division Multiplexing
MIMO - Multiple Input Multiple Output

3G-HSPA+ technology has squeezed a fast capable network from the 3G mobile phone network. But there is still a demand for more speed and more capacity within the network. To do this a new generation of network was proposed that would have a speed of 100Mbps. However 4G was released with a much lower speed capability. By it's nature 4G LTE is an evolution of the previous 3G-HSPA+ technology. There were a number of potentil technologies capable to delivering 4G but the evolution from previous networks was seen as the best solution. The aim of 4G LTE is to achieve higher capacity, reduced latency and more efficient use of the spectrum.

4G LTE is an IP (data) only network with no provision for a separate phone channel. Initially the phone function was covered by the earlier 2G network. Thus to make a phone call the original 4G network would drop the 4G connection and then connect to an available 2G network. This led to early complaints that 4G phones could not make phone calls; the phone was connected to 4G but could not find a suitable 2G network to make the phone call. Subsequently phone calls on the 4G network are made using Vo-LTE technology but still in some areas, where this is not available, a 4G phone will revert to 2g calling. You can tell whether the phone is using 4G calling or 2G calling as on 4G calling "HD" appears on the screen indicating the call is of a higher quality - and you can hear the difference as well.

Two new frequencies were available for the MNOs to bid for in the introduction of 4G. 800MHz was seen as the 4G for rural, or at least non urban, use and 2.6Ghz for city centre use. The 1800MHz frequency is also used for 4G. This frequency was acquired by EE following the takeover / merger of T-Mobile and Orange. They were required by OfCOM to release half of this frequency to THREE. EE claimed that their share of 1800 was spare and were allowed to use this for 4G; subsequently THRE also use 1800MHz for 4G.

As part of the bidding for frequency process, in the UK, one bundle included the additional requirement of a Public Service Obligation - one operator must guarantee a 98% population coverage for 4G. This was purchased by O2.

Typically in a 3G network the communications use the same frequency split into equal size channels. In 4G there is capability to differ the channel size, and use multiple channels even over different frequencies. A mix and match of the technologies to implement this gives 4G better performance as it used the available frequency more efficiently

4G LTE is an evolution of the previous 3G HSPA+ network, and as an IP only network is simplified, compared to 3G, providing better performance. there are 3 key technologies behind 4G :

• SAE - System Architecture Evolution
• OFDM (Orthogonal Frequency Division Multiplexing)
• MIMO (Multiple Input Multiple Output)

SAE - System Architecture Evolution is one of the key technologies behind 4G. In essence it means that the network has been evolved from the previous network(s). The general way 2G 3G and 4G work is the same, as can be seen from the generic network system diagram. In 4G this has led to a simplified network as 4G is an IP based network and has no circuit switching to support phone calls. This speeds up switching significantly. To improve speed some of the core functions are moved to the periphery, there is more processing nearer to the wireless network rather than moving processing to the centre / core. Additionally there have been further efficiency gains in the network functions.