"When looking at the way in which GPRS operates, it can be seen that there are three basic modes in which it operates. These are: initialisation / idle, standby, and ready."

"The BSC assigns PDCHs to particular time slots, and there will be times when the PDCH is inactive, allowing the mobile to check for other base stations and monitor their signal strengths to enable the network to judge when handover is required. The GPRS slot may also be used by the base station to judge the time delay using a logical channel known as the Packet Timing Advance Control Channel (PTCCT).
[...]
The MAC layer is central to this and there are three MAC modes that are used to control the transmissions. These are named fixed allocation, dynamic allocation, and extended dynamic allocation.
[...]
Although GPRS uses only one physical channel (PDCH) for the sending of data, it employs several logical channels that are mapped into this to enable the GPRS data and facilities to be managed."

"The overall slot structure for this channel is the same as that used within GSM, having the same power profile, and timing advance attributes to overcome the different signal travel times to the base station dependent upon the distance the mobile is from the base station. This enables the burst to fit in seamlessly with the existing GSM structure."

"Within GSM there are eight time slots that can be used to provide TDMA, allowing multiple mobiles onto a single RF signal carrier. Within GPRS it is possible to use more than one slot to enable much higher data rates to be achieved when these are available. The different speed classes of the mobiles are dependent upon the number of slots that can be used in either direction."

"The key element of GPRS technology is that it uses packet switched data rather than circuit switched data, and this technique makes much more efficient use of the available capacity. This is because most data transfer occurs in what is often termed a "bursty" fashion. The transfer occurs in short peaks, followed by breaks when there is little or no activity.
[...]
Channel Bandwidth: 200 kHz"

"GPRS uses a packet-mode technique to transfer data and signaling in a cost-efficient manner over GSM radio networks and also optimizes the use of radio and network resources.
[...]
The allocation of these timeslots is flexible, ranging from one to eight timeslots per TDMA frame, and they can be shared by active users. This allows GPRS to handle bitrates from 9 to even up to 150 kbit/s per user."

"In 2G systems, GPRS provides data rates of 56-114 kbit/second.
[...]
It provides moderate speed data transfer, by using unused time division multiple access (TDMA) channels in, for example, the GSM system.
[...]
The upload and download speeds that can be achieved in GPRS depend on a number of factors such as:
- the number of BTS TDMA time slots assigned by the operator
- the maximum capability of the mobile device expressed as a GPRS multislot class
- the channel encoding used summarised in the following table:
[...]
The multiple access methods used in GSM with GPRS are based on frequency division duplex (FDD) and TDMA. During a session, a user is assigned to one pair of up-link and down-link frequency channels. This is combined with time domain statistical multiplexing; i.e., packet mode communication, which makes it possible for several users to share the same frequency channel. The packets have constant length, corresponding to a GSM time slot. The down-link uses first-come first-served packet scheduling, while the up-link uses a scheme very similar to reservation ALOHA (R-ALOHA). This means that slotted ALOHA (S-ALOHA) is used for reservation inquiries during a contention phase, and then the actual data is transferred using dynamic TDMA with first-come first-served scheduling.
[...]
Latency is very high; round-trip time (RTT) is typically about 600-700 ms and often reaches 1 s. GPRS is typically prioritized lower than speech, and thus the quality of connection varies greatly."

"Table 1 shows the different data rates that can be achieved with the different coding techniques."

"... extension on top of standard GSM. EDGE is considered a 3G radio technology and is part of ITU's 3G definition. [...] ...it is an upgrade that provides more than three-fold increase in both the capacity and performance of GSM/GPRS networks.
[...]
EDGE/EGPRS is implemented as a bolt-on enhancement for 2G and 2.5G GSM and GPRS networks, making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade."

"However on the GPRS,the LLC (between MS-SGSN) and RLC/MAC (between MS-
BSS) layer that make up the data link between the MS and the network. The protocol is
mainly an adapted version of the LAPDm protocol used in GSM.The LLC Protocol
establishes a logical link between MS and SGSN. Its functionality includes sequence
control, in-order delivery, flow control,detection of transmission errors, and
retransmission (automatic repeat request (ARQ)). The data confidentiality is ensured by
ciphering functions. It operates either in an unacknowledged mode, not taking care of
packet losses, or in an acknowledged mode, which applies retransmissions and flow
control to ensure a correct delivery of data.

The RLC/MAC layerat the air interface includes two functions. The main purpose of the
radio link control (RLC) layer is to establish a reliable link between the MS and the BSS.
RLC is always operated in an acknowledged mode with a sliding window flow control
mechanism and a selective ARQ mode providing a reliable link between MS and BSS.
This includes the segmentation and reassembly of LLC frames into RLC data blocks and
ARQ of uncorrectable codewords.

This new medium access control (MAC) scheme was changed to meet the demands of the packet oriented data transmission. The RLC/MAC layer ensures the concurrent
access to radio resources in a more flexible way compared to the unmodified TDMA
structure of GSM. It controls the access attempts of an MS on the radio channel shared
by several MSs. It employs algorithms for contention resolution, multiuser multiplexing
on a PDTCH, and scheduling and prioritizing based on the negotiated QoS. The
flexibility is achieved by the introduction of a logical Packet Data Traffic Channel
(PDTCH) which is multiplexed onto a physical data channel, the Packet Data Channel
(PDCH), which corresponds to one timeslot (TS) in the GSM TDMA frame. Up to eight of
these PDTCHs share one PDCH."