Nokia D211 Developer's Manual
Also see for D211: User guideUser guide
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Contents
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11/1132.3.1 HSCSDThe Nokia D211 supports non-transparent data. It also supports High Speed Circuit SwitchedData (HSCSD) in non-transparent mode. With HSCSD a mobile can use several time slots atthe same time. This makes the data transfer rate higher. Time slot usage is presented as thenumber of down links and up link slots. The Nokia D211 data transfer modes are presentedin Table 1.Table 1. The Nokia D211 data transfer modes.Data transfer mode Mode Data rateAsynchronous data 9600 bpsNon-transparent data Asynchronous data 14400 bpsAsynchronous data HSCSD 43200 bps (Multi slot class 6, 3+1)The Nokia D211 supports multi slot class 6 (Max Rx time slots 3, Max Tx time slots 2, sum4). One time slot can be from 9.6 kbit/s to 14.4 kbit/s (network dependent).In HSCSD allocated time slots are reserved only for the user. Other technologies, such asGeneral Packet Radio Service (GPRS), will complement and enhance the value of HSCSD.There are applications for both circuit-switched and packet-switched world. For instance, ifthe user needs to make PSTN/ISDN connection (towards corporate modem pools), onlyHSCSD can be used. HSCSD is ideal for real-time applications and GPRS for "alwaysconnected" applications. For example, HSCSD connections provide "active" e-mail and filetransfer, while GPRS runs in the background for wireless data networking.3+1 operation mode (43.2 + 14.4 kbit/s) is optimal for receiving e-mail, WWW browsing,video streaming, etc. 2+2 operation mode (28.8 + 28.8 kbit/s) is optimal for symmetricapplications such as voice and video calls (e.g. Netmeeting) and e-mail message sending.GSM CSD Modulation CoderateData rate / timeslot (kbit/s)Two slots(kbit/s)Three slots(kbit/s)CSD-3(T/NT) GMSK 0.53 9.6 19.2 28.8CSD-4(T/NT) GMSK 0.64 14.4 28.8 43.22.3.2 GPRSThe nature of packet data is very different from the circuit switched data. GSM was originallydesigned for circuit switched traffic and thus introduction of packet data to GSM meant quitesignificant additions to the GSM network architecture (Figure 4). GPRS interworks with publicdata networks like the Internet (TCP/IP protocol) and X.25 networks. The architecture ofGPRS infrastructure is based on GPRS support nodes, Serving GPRS Support Node(SGSN) and Gateway GPRS Support Node (GGSN), which receive and transmit packetsbetween MSs and terminals connected to public data networks. The support nodes alsoforward packets to those MSs that are not located in the home GSN area. The operation issimilar to the operation of routers in data networks (e.g. the Internet), except that GPRSnodes keep track of the locations of MSs. |
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