Evolved EDGE: E-EDGE

GSM EDGE includes:
GSM EDGE introduction     Network architecture     RF interface     Modulation coding schemes     Evolved EDGE    

Evolved EDGE or E-EDGE is an EDGE evolution that enables 2G EDGE upgraded networks to be able to provide performance equivalent to that of 3G networks like 3G UMTS / WCDMA.

It was also seen as a method for network operators not willing to upgrade to UMTS to provide performance that would match that of the true 3G networks.

Using Evolved EDGE, E-EDGE, speeds of around 1 Mbps were possible, but the actual take-up was very small and it did not reach the critical mass required to make a god impact on the market.

Evolved EDGE, E-EDGE basics

There are a number of new elements that are incorporated onto the original form of EDGE. A number of ideas have been introduced to provide the upgrades required. These include the following:

• Higher Order Modulation:   In order to be able to provide its increase in speed over GPRS, the vanilla version of EDGE uses 8PSK modulation to enable a speed increase. This works by enabling 3 bits to be encoded per symbol. Evolved EDGE, E-EDGE uses higher orders of Quadrature Amplitude Modulation in the forms of 16QAM, which encodes 4 bits per symbol and 32QAM which encodes 5 bits per symbol. That said, 32QAM is only able to be used under ideal conditions because there is a trade-off using higher modulation orders. While they are able to provide higher data rates, they require a greater signal to noise ratio to provide error-free reception.
• Receiver diversity:   The Evolved EDGE system provides for a scheme known as receiver diversity where a second receiver is used to decode the incoming signal a way that can receive it with different characteristics, e.g. position or polarisation. In this way, if the signal on one receiver is poor, there is a chance the signal on the second one is better and can be received with fewer errors.
• Simultaneous channels:   The Evolved EDGE standard allows for the use of two channels, thereby providing the possibility of doubling the throughput.
• Simultaneous transmission and reception:   One key element within GSM, and then GPRS and EDGE, was that to save costs, the Time Division Multiplexing scheme would ensure that the transmitter and receiver in a mobile handset were never active at the same time. This was achieved by using one slot for transmission, and a different time slot for reception. Even when multiple slots are used, one either side of the reception slot(s) was kept clear to allow for transmit / receive settling.
  
  Evolved EDGE allows for simultaneous transmission and reception as the cost of more effective filtering between the transmitter and receiver. Most EDGE mobiles on the market are restricted to four timeslots per carrier due to this phenomenon, having independent transmission and reception chains could allow mobiles to use all eight timeslots of a carrier.

The EDGE evolution did not see an enormous level of take-up. There was a move to 3G technologies and the evolution to HSPA. This provided a much better evolution than building onto a system that started to be seen as out-dated.

Both phone manufacturers and operators alike wanted to be able to move to 3G and then ultimately on to 4G. Although Evolved EDGE would provide many advantages, it was not able to provide the long term benefits that a move to the other technologies would provide.

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