13/113
GPRS-2 (Phase 1 network). This means that at the moment
13.4 kbit/s is the maximum
speed for one time slot.
3+1: 40.2 kbit/s + 13.4 kbit/s.
2+2: 26.8 kbit/s + 26.8 kbit/s
It is also important to remember that peak bit rate is only one part to the actual end user
experienced performance.
GPRS
Modulation
Code
rate
Data rate /
time slot (kbit/s)
Two slots
(kbit/s)
Three slots
(kbit/s)
GPRS-1 GMSK 0.50 9.05
18.1
27.15
GPRS-2 GMSK 0.64 13.4
26.8
40.2
GPRS-3 GMSK 0.74 15.6
31.2
46.8
GPRS-4 GMSK 1.00 21.4
42.8
64.2
2.3.3 Terminal
classes
Three classes of GPRS MSs have been defined:
•
Class-A MS can operate GPRS and other GSM services simultaneously
•
Class-B MS can monitor control channels for GPRS and other GSM services
simultaneously, but can only operate one set of services at one time
•
Class-C GPRS MS can exclusively operate GPRS services.
The Nokia D211 is a class B terminal.
The Nokia D211 can be attached to GSM and GPRS services simultaneously. Data calls can
be received during GPRS activity. No data calls, however, are possible when GPRS data
transmission is active, and no GPRS data transmission is possible when a data call is active
-> GPRS is put to suspend mode when there is an active data call.
2.3.4 GPRS
security
GPRS security functionality is equivalent to the existing GSM security. The SGSN performs
authentication and cipher setting procedures based on the same algorithms, keys, and
criteria as in existing GSM. GPRS uses a ciphering algorithm optimised for packet data
transmission. However, as GPRS data packets are transmitted using the Internet, VPN
(Virtual Private Network) is recommended for end-to-end security in corporate networks.
2.3.5 GPRS
summary
Data rates depend on the availability of channels in use per cell and on the channel quality.
In weak channel conditions more protection (stronger channel coding) for user data bits is
needed and this naturally means that less user data bits can be sent in a given time period.
In good channel conditions the situation is obviously the opposite. The theoretical maximum
data rate in GPRS is 64.2 kbit/s. The uplink and downlink data rates are asymmetric as in
HSCSD.
