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Claims  |
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What is claimed is:
1. An apparatus for providing packet data communication to and from mobile
stations in a digital TDMA cellular system having a plurality of base
stations providing regular cellular control channels and regular cellular
dedicated traffic channels; one or more mobile services switching centers,
each being associated with a visitor location register and being coupled
to a subordinated plurality of the base stations; and home location
register means for storing information on mobile station subscribers, the
apparatus comprising:
channel providing means for providing, in at least some of the base
stations, on a per cell basis, one or more shared packet data channels for
packet transfer to and from the mobile stations, and packet transfer
controlling means for controlling the packet transfer;
channel defining means for defining, on a per cell basis, the packet data
channel to be used for packet transfer;
first packet data mode establishing means for establishing packet data mode
for a mobile station to enable the mobile station to send and receive
packets over the packet data channels;
first packet transferring means for transferring packets between the mobile
stations and base stations;
second packet transferring means for transferring packets between the base
stations and their respective superior mobile services switching centers;
packet routing means for routing packets to and from a service area of a
mobile services switching center;
first means for performing cell selection for a mobile station in packet
data mode;
first means for performing location updating for the mobile station in
packet data mode;
first packet data mode maintaining means for maintaining the packet data
mode for a roaming mobile station; and
first packet data mode terminating means for terminating the established
packet data mode for the mobile station.
2. The apparatus of claim 1, wherein the channel defining means comprises
first information supplying means for supplying, on a regular cellular
broadcast control channel, information defining the packet data channel to
be used for initiating packet transfer, if such a packet data channel is
provided in the cell.
3. The apparatus of claim 2, wherein the channel defining means further
comprises second information supplying means for supplying, on a regular
cellular broadcast control channel, information indicating that a packet
data channel for initiating packet transfer may be provided by the channel
providing means on user demand.
4. The apparatus of claim 1, wherein the means for performing cell
selection is adapted to perform cell selection based on regular cellular
idle mode procedures.
5. The apparatus of claim 4, wherein the means for performing cell
selection comprises means for retaining a currently selected cell as long
as the signal quality is above a predefined threshold value.
6. The apparatus of claim 4, wherein the first packet transferring means
and the first means for performing cell selection, to coordinate
initiating packet transfers to mobile stations with performing cell
selection in the mobile stations, comprise means for scheduling paging and
other messages initiating packet transfers to mobile stations according to
a multi-TDMA frame scheme synchronized with corresponding multiframe
schemes used for regular cellular control channel signalling, allowing
predefined times for mobile stations to perform cell selection and to
receive regular cellular broadcast messages.
7. The apparatus of claim 1, wherein the first means for performing
location updating is adapted to perform location updating based on regular
cellular idle mode procedures.
8. The apparatus of claim 1, wherein the first packet data mode
establishing means comprises:
means for initiating the establishment of packet data mode for a mobile
station from an initial cellular idle mode, either by the mobile station
generating a packet data service request based on regular cellular control
channel signalling, or by the mobile services switching center currently
serving the mobile station receiving a packet addressed to the mobile
station and paging the mobile station based on regular cellular control
channel signalling;
means for performing a regular cellular authentication procedure after
packet data mode establishment has been initiated;
means for initiating parameters for packet encryption/decryption between
the mobile station and the mobile services switching center currently
serving the mobile station; and
means for registering the mobile station at its current mobile services
switching center with associated visitor location register as being in
packet data mode.
9. The apparatus of claim 1, wherein the channel providing means comprises:
means for allocating, from a common pool of physical channels, a variable
mix of packet data channels and regular cellular traffic channels
determined by demand;
means for assigning a first packet data channel allocated in a cell as a
channel for initiating packet transfer, capable of carrying access control
signalling as well as packet data; and
means for assigning a further allocated packet data channel as a channel
for reserved packet transfer.
10. The apparatus of claim 9, wherein the channel providing means is
adapted to allocate the first packet data channel in a cell on user
demand, and comprises:
means for allocating a packet data channel as a result of a successful
packet data mode establishment; and
means for allocating a packet data channel based on regular cellular
control channel signalling, initiated by one of a mobile station in packet
data mode generating a packet data channel allocation request, or a
successful paging to a mobile station in packet data mode.
11. The apparatus of claim 9, wherein the channel providing means is
adapted to allocate the first packet data channel in a cell on user
demand, and comprises means for allocating a packet data channel,
initiated by a mobile station in packet data mode that generates a packet
data channel allocation request for the cell prior to the mobile station's
moving into the cell, using a packet data channel of a currently serving
adjacent cell.
12. The apparatus of claim 9, wherein the channel providing means further
comprises:
means for dynamically allocating a variable number of the packet data
channels for initiating packet transfer such that a group of these
channels can be used together with a common group of packet data channels
for reserved packet transfer; and
means for directing the mobile station to a particular one of the packet
data channels for initiating packet transfer, if more than one such
channel is allocated, based on mobile station identity and broadcast
control information.
13. The apparatus of claim 1, wherein the first and second packet
transferring means, for initiating a packet transfer to a mobile station
in packet data mode, comprise paging means and monitoring means for
monitoring a cell location of the mobile station based on a previous
packet transfer, and the first and second packet transferring means are
adapted for paging guided by the monitoring means to initiate a packet
transfer to a mobile station.
14. The apparatus of claim 13, wherein the monitoring means comprises:
means for identifying a cell location of a mobile station originating a
packet by, when the packet is received at the mobile services switching
center currently serving the mobile station, associating the packet with
the identity of a connection on which the packet is received, the
connection being unique for each cell;
means for identifying a cell location of a mobile station responding to a
paging message; and
means for storing for a mobile station, linked to the mobile station's
packet mode registration, at least a latest cell location identified and
an associated time when the cell location was identified.
15. The apparatus of claim 13, wherein the first and second packet
transferring means, for initiating a packet transfer to a mobile station,
further comprise means for monitoring a mobile/stationary mode indicator
sent by a mobile station capable of operating in a stationary mode to its
currently serving mobile services switching center at least every time the
mobile station changes from mobile mode to stationary mode and vice versa.
16. The apparatus of claim 15, wherein the first and second packet
transferring means are adapted to, to a mobile station that is in
stationary mode and performs cell selection based on regular cellular idle
mode procedures, initiate packet transfers without previous paging or with
paging in a single cell.
17. The apparatus of claim 15, wherein the first and second packet
transferring means are adapted to initiate packet transfers to a mobile
station that is in mobile mode and performs cell selection based on
regular cellular idle mode procedures without previous paging or with
paging in a single cell, provided that cell location information from the
monitoring means meets predefined accuracy criteria.
18. The apparatus of claim 1, wherein the first and second packet
transferring means, for initiating packet transfers to mobile stations in
packet data mode, comprise paging means adapted to include a paging
message type combining a paging request with reservation of an individual
access slot for the mobile station to respond.
19. The apparatus of claim 1, wherein the first and second packet
transferring means comprise paging means adapted to convey, on a packet
data channel, paging messages related to regular cellular calls to a
mobile station in packet data mode.
20. The apparatus of claim 1, wherein the first packet data mode
maintaining means comprises:
means for allowing a mobile station in packet data mode to make and receive
regular cellular calls;
means for maintaining packet data mode as pending during a regular cellular
call; and
means for returning the mobile station to active packet data mode when the
regular cellular call is completed.
21. The apparatus of claim 1, wherein the packet routing means comprises:
one or more interworking function means for internetworking with at least
one external network;
interconnection means for interconnecting the interworking function means
and mobile services switching centers; and
means for routing packets, addressed to a mobile station, from any of the
interworking function means to a mobile services switching center
currently serving the mobile station, the means for routing packets
including:
at the interworking function means, means for determining from stored
routing information whether a route to the mobile station's currently
serving mobile services switching center is established, linked to an
identity of the mobile station; means for routing packets to the currently
serving mobile services switching center when a route is established; and
means, when a route is not established, for initially interrogating the
home location register means to determine the identity of the mobile
services switching center currently serving the mobile station, and for
storing, linked to the identity of the mobile station, the identity of the
currently serving mobile services switching center; and
at the currently serving mobile services switching center, means for
initiating establishment of packet data mode for the mobile station when
packet data mode is not already established, and means for initially
determining and storing, linked to a packet data mode registration of the
mobile station, an identity of the interworking function means.
22. The apparatus of claim 21, wherein the packet routing means, for
maintaining routes established to a mobile station's currently serving
mobile services switching center when the mobile station moves to a
location area belonging to a new mobile services switching center,
comprises means for updating at least one of interworking function means
and mobile services switching centers of any routes established about the
change from the currently serving mobile services switching center to the
new mobile services switching center, initiated from the new mobile
services switching center, based on information provided by the first
packet data mode maintaining means.
23. The apparatus of claim 21, wherein the packet routing means comprises:
at the mobile station's currently serving mobile services switching center,
means for monitoring, as to traffic activity, a route established to the
currently serving mobile services switching center, linked to the packet
data mode registration of the mobile station, and means for initiating
termination of the route when the traffic activity falls below a
predetermined level; and
at at least one of an interworking function means and a mobile services
switching center of the route, means for cancelling related routing
information when termination of the route is initiated.
24. The apparatus of claim 1, wherein the packet routing means comprises:
interconnection means for interconnecting mobile services switching
centers; and
means for routing packets originated from a first mobile station and
addressed to a second mobile station, including:
at the mobile services switching center currently serving the first mobile
station, means for determining from stored routing information whether a
route to the mobile services switching center currently serving the second
mobile station is established, linked to a packet data mode registration
of the first mobile station; means for routing packets to the second
mobile station's currently serving mobile services switching center when a
route is established; and means for initially interrogating the home
location register means to determine an identity of the mobile services
switching center currently serving the second mobile station when a route
is not established, and for storing, as routing information, the identity
of the second mobile station's currently serving switching center with the
identity of the second mobile station, linked to the packet data mode
registration of the first mobile station; and
at the mobile services switching center currently serving the second mobile
station, means for initiating establishment of packet data mode for the
second mobile station when packet data mode is not already established,
and means for initially determining and storing, linked to the packet data
mode registration of the second mobile station, an identity of the first
mobile station and an identity of the mobile services switching center
currently serving the first mobile station.
25. The apparatus of claim 1, wherein the packet routing means comprises:
interconnection means for interconnecting mobile services switching
centers, and for connecting one or more mobile services switching centers
to at least one external network;
means for routing packets addressed to a mobile station from an external
network or another mobile station to an addressed mobile services
switching center to which the mobile station belongs for packets addressed
to the mobile station; and
means for routing packets addressed to a mobile station from the addressed
mobile services switching center to a mobile services switching center
currently serving the mobile station, including:
at the addressed mobile services switching center, means for determining
from stored routing information whether a route to the mobile station's
currently serving mobile services switching center is established, linked
to an identity of the mobile station; means for routing packets to the
currently serving mobile services switching center when a route is
established; and means for initially interrogating the home location
register means, when a route is not established, to determine an identity
of the currently serving mobile services switching center, and for
storing, as routing information, the identity of the currently serving
mobile services switching center linked to the identity of the mobile
station; and
at the currently serving mobile services switching center, means for
initiating establishment of packet data mode for the mobile station when
packet data mode is not already established, and means for initially
determining and storing, linked to the packet data mode registration of
the mobile station, an identity of the addressed mobile services switching
center.
26. The apparatus of claim 1, wherein the first packet data mode
maintaining means, for maintaining packet data mode for a mobile station
when the mobile station moves to a location area belonging to a new mobile
services switching center, comprises means for transferring a packet data
mode registration and associated information, stored at the mobile
station's currently serving mobile services switching center, from the
currently serving mobile services switching center to the new mobile
services switching center, initiated from the new mobile services
switching center, based on information provided by the means for
performing location updating.
27. The apparatus of claim 1, wherein the first packet data mode
terminating means comprises means for monitoring a mobile station as to
traffic activity, and means for terminating packet data mode and a route
established to the mobile station's currently serving mobile services
switching center when the traffic activity falls below a predetermined
level.
28. The apparatus of claim 1, wherein the first packet data mode
terminating means comprises means for monitoring a time elapsed since
packet data mode was established for a mobile station, and means for
terminating packet data mode and an associated route established to the
mobile station's currently serving mobile service's switching center when
the time elapsed exceeds a predetermined period of time.
29. A mobile station for packet data communication over digital TDMA
cellular shared packet data channels provided by the apparatus according
to claim 1, comprising:
channel identifying means for identifying, on a per cell basis, the packet
data channel to be used for initiating packet transfer;
second packet data mode establishing means for establishing packet data
mode for the mobile station to enable the mobile station to send and
receive packets over the packet data channels;
means for sending and receiving packets over the packet data channels;
second means for performing cell selection in packet data mode;
second means for performing location updating in packet data mode;
second packet data mode maintaining means for maintaining the packet data
mode for the mobile station; and
second packet data mode terminating means for terminating the established
packet data mode for the mobile station.
30. The mobile station of claim 29, wherein the channel identifying means
is adapted to read, from a regular cellular broadcast control channel,
information supplied for defining a packet data channel to be used for
initiating packet transfer.
31. The mobile station of claim 30, wherein the channel identifying means
is adapted to read, from a regular cellular broadcast control channel,
information supplied for indicating that the packet data channel for
initiating packet transfer may be provided on user demand.
32. The mobile station of claim 29, wherein the second means for performing
cell selection is adapted to perform cell selection based on regular
cellular idle mode procedures.
33. The mobile station of claim 32, wherein the second means for performing
cell selection comprises means for retaining a currently selected cell as
long as the signal quality is above a predefined threshold value.
34. The mobile station of claim 32, wherein the means for sending and
receiving packets and the second means for performing cell selection, to
coordinate listening to a packet data channel on which packet transfers to
the mobile station are initiated with performing cell selection, comprise
means for scheduling listening for paging and other messages initiating
packet transfers to the mobile station according to a multi-TDMA frame
scheme synchronized with corresponding multiframe schemes used for regular
cellular control channel signalling allowing predefined times for the
mobile station to perform cell selection and to receive regular cellular
broadcast messages.
35. The mobile station of claim 29, wherein the second means for performing
location updating is adapted to perform location updating based on regular
cellular idle mode procedures.
36. The mobile station of claim 29, wherein the second packet data mode
establishing means comprises:
means for initiating establishment of packet data mode in the mobile
station, from an initial cellular idle mode, by one of the mobile
station's generating a packet data service request based on regular
cellular control channel signalling, or the mobile stations receiving a
paging message based on regular cellular control channel signalling,
indicating that a packet, addressed to the mobile station, has been
received by a mobile services switching center currently serving the
mobile station;
means for performing a regular cellular authentication procedure after
packet data mode establishment has been initiated;
means for initiating parameters for packet encryption/decryption in the
mobile station; and
means for storing, for the mobile station, information indicating that
packet data mode is established.
37. The mobile station of claim 29, further comprising means, when the
mobile station is in packet data mode and is located in a cell providing a
packet data channel on user demand, for generating a packet data channel
allocation request based on regular cellular control channel signalling.
38. The mobile station of claim 29, further comprising means, when the
mobile station is in packet data mode and is located in a currently
serving cell with a packet data channel allocated, for generating a packet
data channel allocation request for an adjacent cell providing packet data
channel on user demand, prior to moving into the adjacent cell, using a
packet data channel of the currently serving cell.
39. The mobile station of claim 29, wherein the means for sending and
receiving packets comprises means for sending a mobile/stationary mode
indicator to a mobile services switching center currently serving the
mobile station at least every time the mobile station changes from mobile
mode to stationary mode and vice versa.
40. The mobile station of claim 29, wherein the means for sending and
receiving packets comprises means for responding to a paging message type
combining a paging request with reservation of an individual access slot
for the mobile station to respond.
41. The mobile station of claim 29, wherein the means for sending and
receiving packets comprises means for responding to a paging message
received on a packet data channel and related to a regular cellular call.
42. The mobile station of claim 29, wherein the second packet data mode
maintaining means comprises means for allowing the mobile station to make
and receive regular cellular calls when being in packet data mode;
means for maintaining packet data mode as pending during a regular cellular
call; and
means for returning the mobile station to active packet data mode when the
regular cellular call is completed.
43. An apparatus for providing packet data communication to and from mobile
stations, utilizing a plurality of base stations of a digital TDMA
cellular system that provide regular cellular control channels and regular
cellular dedicated traffic channels, comprising:
channel providing means for providing, in at least some of the base
stations, one or more shared packet data channels for packet transfer to
and from the mobile stations, and packet transfer controlling means for
controlling the packet transfer;
channel defining means for defining, on a per cell basis, the packet data
channel to be used for packet transfer;
packet transferring means for transferring packets between mobile stations
and base stations;
coupling means for coupling the packet transfer controlling means to a
separate mobile packet data infrastructure comprising packet routing
means, for routing packets to and from a service area of a mobile
switching center, and mobility management means, for managing location and
routing information for the mobile stations; and
first means for performing cell selection for the mobile stations.
44. The apparatus of claim 43, wherein the channel defining means comprises
information supplying means for supplying, on a regular cellular broadcast
control channel, information defining the packet data channel to be used
for initiating packet transfer, if such a packet data channel is provided
in the cell.
45. The apparatus of claim 43, wherein the first means for performing cell
selection is adapted to perform cell selection based on regular cellular
idle mode procedures.
46. The apparatus of claim 45, wherein the first means for performing cell
selection comprises means for retaining a currently selected cell as long
as the signal quality is above a predefined threshold value.
47. The apparatus of claim 43, wherein the channel providing means
comprises:
means for allocating, from a common pool of physical channels, a variable
mix of packet data channels and regular cellular traffic channels
determined by demand;
means for assigning a first packet data channel allocated in a cell as the
channel for initiating packet transfer, capable of carrying access control
signals and packet data; and
means for assigning a further allocated packet data channel as a channel
for reserved packet transfer.
48. The apparatus of claim 47, wherein the channel providing means
comprises:
means for dynamically allocating a variable number of the packet data
channels for initiating packet transfer such that a group of these
channels can be used together with a common group of packet data channels
for reserved packet transfer; and
means for directing a mobile station to a particular one of the packet data
channels for initiating packet transfer, if more than one such channel is
allocated, based on an identity of the mobile station and on broadcast
control information.
49. The apparatus of claim 43, wherein the packet transferring means, for
initiating packet transfers to mobile stations, comprises paging means
adapted to include a paging message type combining a paging request with
reservation of an individual access slot for the mobile station to
respond.
50. The apparatus of claim 43, wherein the packet transferring means and
the first means for performing cell selection, to coordinate initiating
packet transfers to mobile stations with performing cell selection in the
mobile stations, comprise means for scheduling messages initiating packet
transfers to mobile stations according to a multi-TDMA frame scheme
synchronized with corresponding multiframe schemes used for regular
cellular control channel signalling, allowing predefined times for mobile
stations to perform cell selection and to receive regular cellular
broadcast messages.
51. A mobile station for packet data communication over digital TDMA
cellular shared packet data channels provided by the apparatus of claim
43, comprising:
channel identifying means for identifying, on a per cell basis, the packet
data channel to be used for initiating packet transfer;
means for sending and receiving packets over the packet data channels; and
second means for performing cell selection.
52. The mobile station of claim 51, wherein the channel identifying means
is adapted to read, from a regular cellular broadcast control channel,
information supplied for defining a packet data channel to be used for
initiating packet transfer.
53. The mobile station of claim 51, wherein the means for sending and
receiving packets comprises means for sending a mobile/stationary mode
indicator to the separate mobile packet data infrastructure at least every
time the mobile station changes from mobile mode to stationary mode and
vice versa.
54. The mobile station of claim 51, wherein the means for sending and
receiving packets comprises means for responding to a paging message type
combining a paging request with a reservation of an individual access slot
for the mobile station to respond.
55. The mobile station of claim 51, wherein the second means for performing
cell selection is adapted to perform cell selection based on regular
cellular idle mode procedures.
56. The mobile station of claim 55, wherein the second means for performing
cell selection comprises means for retaining a currently selected cell as
long as the signal quality is above a predefined threshold value.
57. The mobile station of claim 55, wherein the means for sending and
receiving packets and the second means for performing cell selection, to
coordinate listening to the packet data channel on which packet transfers
to the mobile station are initiated with performing cell selection,
comprise means for scheduling listening for messages initiating packet
transfers to the mobile station according to a multi-TDMA frame scheme
synchronized with corresponding multiframe schemes used for regular
cellular control channel signalling, allowing predefined times for the
mobile station to perform cell selection and to receive regular cellular
broadcast messages. |
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Claims |
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Description |
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BACKGROUND
This invention relates to digital TDMA (Time Division Multiple Access)
cellular radio mobile telecommunications systems. More specifically, the
present invention is directed towards apparatuses and mobile stations for
providing packet data communications services in current TDMA cellular
systems.
Mobile data communication is rapidly becoming one of the fastest growing
segments of the mobile communications market. Independent market studies
predict several million users in Europe by the year 2000. A strong driving
force is the fast growing portable personal ("laptop", "palmtop" and
"notebook") computer market and the need for flexible wireless data
communications it creates. This market force is further emphasized by the
emerging new communication-centered devices, commonly referred to as
"Personal Digital Assistants" or "Personal Communicators". Target
applications include:
The wide range of standard business applications today predominantly used
across fixed data networks, such as electronic mail and host computer/data
base access.
Specialized mobile data applications including vehicle fleet control and
road transport informatics.
Fixed wireless applications, including remote monitoring and control
applications, and credit card verification and similar financial
transaction applications.
Possible new applications as a result of the convergence of the two
enabling technologies of new personal computing/communicating devices and
efficient and widely available mobile data communications.
To support this variety of applications in a cost effective manner, a
mobile data network should:
Provide packet mode data services based on shared packet data radio
channels optimized for packet data (exploiting the bursty nature of most
data communications applications) to achieve spectrum efficiency and cost
effectiveness.
Provide industry standard network services, including standard
connectionless network (datagram) services and, depending on market
requirements, standard connection-oriented network (virtual call) services
e.g. to provide transparent X.25 connectivity.
Provide performance (packet transfer delays) comparable to what is provided
by current fixed networks, to allow existing standard applications to be
used without modification.
Provide broadcast and multicast services to support specialized mobile
applications.
Providing the packet data services on a cellular system platform offers
potential advantages in terms of widespread availability, possibility of
combined voice/data services, and comparatively low additional investments
by capitalizing on the cellular infrastructure. Of particular interest are
current TDMA cellular systems, through their spectrum efficiency and world
wide penetration. Examples of potential TDMA platforms include:
GSM (Global System for Mobile communication)
Systems with a GSM type of architecture but operating in other frequency
bands, such as the 1800 and 1900 MHz bands, including PCN (Personal
Communications Network) in Europe and PCS (Personal Communications
Services) in the U.S.A.
The North American D-AMPS (Digital Advanced Mobile Phone Service) system.
The Japanese PDC (Personal Digital Cellular) system.
However, the data services provided by or proposed for cellular systems in
general are with few exceptions based on circuit mode of operation, using
a dedicated radio channel for each active mobile user. The exceptions
include the packet data concepts described in the following documents:
a) U.S. Pat. No. 4,887,265 and Proc. 38th IEEE Vehicular Technology
Conference, June 88, Philadelphia (U.S.), pages 414-418: "Packet Switching
in Digital Cellular Systems".
These documents describe a cellular system providing shared packet data
radio channels, each one capable of accomodating multiple data calls. A
mobile station requesting packet data service is assigned to a particular
packet data channel using essentially regular cellular signalling. The
system may include Packet Access Points (PAPs) for interfacing with packet
data networks. In that case, each packet data radio channel is connected
to one particular PAP and is thus capable of multiplexing data calls
associated with that PAP. System initiated handover (handoff) is employed,
to a large extent similar to the type of handover used in the same system
for voice calls. A new type of handover is added for handling situations
when the capacity of a packet channel is insufficient.
b) U.S. Pat. No. 4,916,691.
This document describes (for one of the embodiments) a new packet mode
cellular radio system architecture, and a new procedure for routing (voice
and/or data) packets to a mobile station. Base stations, public switches
via trunk interface units, and a cellular control unit are linked together
via a wide area network. The routing procedure is based on mobile station
initiated handover and on adding to the header of any packet transmitted
from a mobile station (during a call) an identifier of the base station
through which the packet passes. In case of an extended period of time
between subsequent user information packets from a mobile station, the
mobile station may transmit extra control packets for the sole purpose of
conveying cell location information. The cellular control unit is
primarily involved at call establishment, when it assigns to the call a
call control number. It then notifies the mobile station of the call
control number and the trunk interface unit of the call control number and
the identifier of the initial base station. During a call, packets are
then routed directly between the trunk interface unit and the currently
serving base station.
c) Cellular Digital Packet Data (CDPD) System Specification, Release 1.0,
July, 1993.
CDPD is a new concept for providing packet data services, utilizing
available radio channels on current Advanced Mobile Phone Service AMPS
systems (i.e. the North American Analog Cellular System). CDPD is a
comprehensive, open specification endorsed by a group of U.S. cellular
operators. Items covered include external interfaces, air interfaces,
services, network architecture, network management, and administration.
The CDPD system specified is to a large extent based on an independent
infrastructure. Common denominators with AMPS systems are limited to
utilization of the same type of radio frequency channels and the same base
station sites (the base station itself, used by CDPD, is new and CDPD
specific), and employment of a signalling interface for coordinating
channel assignments between the two systems. Routing a packet to a mobile
station is based on, first routing the packet to a home network node (home
Mobile Data Intermediate System, MD-IS) equipped with a home location
register (HLR), based on the mobile station address; then, when necessary,
routing the packet to a visited, serving MD-IS based on HLR information;
and finally transferring the packet from the serving MD-IS via the current
base station, based on the mobile station reporting its cell location to
its serving MD-IS.
d) ETSI (European Telecommunications Standards Institute) T Doc SMG 4
58/93, Feb. 12, 1993: "Packet Radio in GSM"; and "GSM in a future
competitive environment", seminar, Helsinki, Oct. 13, 1993: "A General
Packet Radio Service Proposed for GSM".
These documents outline a possible packet access protocol for voice a | | |
