Editing EDGE (telecommunication) (section)

== Evolved EDGE ==
'''Evolved EDGE''', also called '''EDGE Evolution''' and '''2.875G''', is a bolt-on extension to the [[GSM]] mobile telephony standard, which improves on EDGE in a number of ways. Latencies are reduced by lowering the [[Transmission Time Interval]] by half (from 20 ms to 10 ms). Bit rates are increased up to 1&nbsp;Mbit/s peak bandwidth and latencies down to 80 ms using dual carrier, higher symbol rate and [[higher-order modulation]] (32QAM and 16QAM instead of 8PSK), and [[turbo code]]s to improve error correction. This results in real world downlink speeds of up to 600&nbsp;kbit/s.<ref>{{cite web |url=http://developer.att.com/devcentral/tools_technologies/network/docs/DataCapabilities_GPRS__to_HSDPA.pdf |title=EDGE, HSPA and LTE: The Mobile Broadband Advantage |publisher=Rysavy Research and 3G Americas |pages=58–65 |date=2007-09-01 |access-date=2010-09-27 |archive-url=https://web.archive.org/web/20091007091901/http://developer.att.com/devcentral/tools_technologies/network/docs/DataCapabilities_GPRS__to_HSDPA.pdf |archive-date=2009-10-07}}</ref> Further the signal quality is improved using dual antennas improving average bit-rates and spectrum efficiency.

The main intention of increasing the existing EDGE throughput is that many operators would like to upgrade their existing infrastructure rather than invest on new network infrastructure. Mobile operators have invested billions in GSM networks, many of which are already capable of supporting EDGE data speeds up to 236.8&nbsp;kbit/s. With a software upgrade and a new device compliant with Evolved EDGE (like an Evolved EDGE [[smartphone]]) for the user, these data rates can be boosted to speeds approaching 1&nbsp;Mbit/s (i.e. 98.6&nbsp;kbit/s per timeslot for 32QAM). Many service providers may not invest in a completely new technology like [[3G]] networks.<ref name="engadgetmobile.com">{{cite web|url=https://www.engadget.com/2009-09-14-nokia-siemens-fires-off-first-edge-evolution-downlink-dual-carri.html |author=Chris Ziegler|date=Sep 14, 2009|title=Nokia Siemens fires off first EDGE Evolution Downlink Dual Carrier trial |website=www.engadgetmobile.com|access-date=2016-03-14}}</ref>

Considerable research and development happened throughout the world for this new technology. A successful trial by Nokia Siemens and "one of China's leading operators" was achieved in a live environment.<ref name="engadgetmobile.com"/> However, Evolved EDGE was introduced much later than its predecessor, EDGE, coinciding with the widespread adoption of 3G technologies such as [[High Speed Packet Access|HSPA]] and just before the emergence of [[4G]] networks. This timing significantly limited its relevance and practical application, as operators prioritized investment in more advanced wireless technologies like [[UMTS]] and [[LTE (telecommunication)|LTE]].

Moreover, these newer technologies also targeted network coverage layers on low frequencies, further diminishing the potential advantages of Evolved EDGE. Coupled with the upcoming phase-out and shutdown of 2G mobile networks, it became very unlikely that Evolved EDGE would ever see deployment on live networks. As of 2016, no [[Cellular network|commercial networks]] supported the Evolved EDGE standard (3GPP Rel-7).

=== Technology ===

==== Reduced Latency ====
With Evolved EDGE come three major features designed to reduce latency over the air interface.

In EDGE, a single RLC data block (ranging from 23 to 148 bytes of data) is transmitted over four frames, using a single time slot. On average, this requires 20 ms for one way transmission. Under the RTTI scheme, one data block is transmitted over two frames in two timeslots, reducing the latency of the air interface to 10 ms.

In addition, Reduced Latency also implies support of Piggy-backed [[ACK (TCP)|ACK]]/[[NACK]] (PAN), in which a bitmap of blocks not received is included in normal data blocks. Using the PAN field, the receiver may report missing data blocks immediately, rather than waiting to send a dedicated PAN message.

A final enhancement is RLC-non persistent mode. With EDGE, the RLC interface could operate in either acknowledged mode, or unacknowledged mode. In unacknowledged mode, there is no retransmission of missing data blocks, so a single corrupt block would cause an entire upper-layer IP packet to be lost. With non-persistent mode, an RLC data block may be retransmitted if it is less than a certain age. Once this time expires, it is considered lost, and subsequent data blocks may then be forwarded to upper layers.

==== Higher modulation schemes ====
Both uplink and downlink throughput is improved by using 16 or 32 QAM (quadrature amplitude modulation), along with turbo codes and higher symbol rates.