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Mobile Phone Patent Abstract
A mobile phone with a basic unit provided with a memory necessary
for the processing of speech signals only, whereby the processing
of the possible data signals is carried out in an auxiliary unit
connected to the interface, the auxiliary unit comprising the memory
required for the processing of the data signals.
Mobile Phone Patent Claims
What is claimed is:
1. A circuit arrangement for a mobile telephone operating according
to a digital mobile telephone system comprising:
a speech only module including:
a transmission function module including speech coding means for
converting speech into compressed digital form, channel coding means
for generating error correction patterns and combining the error
correction patterns with the compressed digitized speech, and multiplexing
means for arranging digital bits of the combined error correction
patterns and compressed digitized speech into appropriate time slots
of a multiplexed signal;
a receiver function module including demultiplexing/channel decoding
means for extracting speech information from the multiplexed signal
and performing error correction;
a transmitter/receiver function module including modulating means
for modulating the multiplexed signal according to a digital mobile
telephone standard;
a memory unit having a first storage capacity no larger than that
necessary to accommodate a speech-only call between the mobile telephone
and the mobile telephone system; and
a central processing unit for controlling the circuit arrangement
and storing information in the memory unit; and
an adaptor unit connected to the speech-only module the adaptor
unit having encoding and decoding means for transmission and reception
of non-speech data information from the speech-only module and an
auxiliary memory unit having a second storage capacity, the combined
storage capacity of the memory unit and auxiliary memory unit being
at least sufficient to maintain a speech and data call between the
mobile telephone and the mobile telephone system.
2. The circuit of claim 1, further including an interface for connecting
the adaptor unit to the transmitter/receiver function module and
the central processing unit.
3. The circuit of claim 2, wherein the interface is a fast bus
interface.
4. The circuit of claim 1, wherein the memory unit and auxiliary
memory unit are random access memories.
5. The circuit of claim 1, wherein a majority of the storage capacity
of the memory unit and auxiliary memory unit hold data for channel
decoding and demultiplexing, the memory unit having a storage capacity
less than half the size of the auxiliary memory unit.
6. The circuit of claim 1, wherein the auxiliary memory unit is
sufficient alone to maintain a speech and data call between the
mobile telephone and the mobile telephone system.
7. The circuit of claim 1, wherein the adaptor unit is selectively
connectable to the mobile telephone via the interface.
8. The circuit of claim 1, wherein the adaptor unit includes a
data interface to receive data signals from a data terminal to be
connected to the mobile telephone.
Mobile Phone Patent Description
FIELD OF THE INVENTION
The present invention relates generally to communication systems
and, more specifically, to a mobile telephone capable of both speech
and data communication in a digital mobile telephone system.
BACKGROUND OF THE INVENTION
Mobile telephone use has evolved into a critical communication
link for information flow. Originally, mobile telephones were capable
of transmitting and receiving only speech signals. The proliferation
of data transmission, such as facsimile and computer information,
made it necessary for mobile telephones to be capable of both speech
and data communication. This additional capability has been achieved
primarily through the use of digital telephone network that are
capable of converting analog speech signals to digital signals and
combining them with the digital data signals. Examples of such digital
telephone networks are the Pan-European digital mobile system Groupe
Special Mobile (GSM) and a proposed U.S. system. The mobile digital
telephone systems typically employ a type of time division multiplexing
or "burst" communication where each burst contains several
bits of digital information arranged according to a frame format
defined in the standard for the system. Frames of information are
divided into time slots, with each time slot being one or to more
bits. The information conveyed in the time slots can be speech,
data, or control signals.
The control signals determine whether a speech-only call or a speech
and data call will be established between the mobile telephone and
the mobile telephone system. In a speech-only call, the mobile telephone
need only extract the appropriate time slot information designated
as speech information according to the frame format. In a speech
and data call, the mobile telephone must extract the appropriate
signals from the speech time slots as well as from the data time
slots. The received speech or speech and data information must then
be stored in memory for processing by the mobile telephone. It is
thus seen that a speech-only mobile telephone requires less memory
than a speech and data telephone. A mobile telephone's memory is
costly and consumes considerable power, thus, there is a need for
mobile telephone circuit arrangements that provide speech or speech
and data capabilities while at the same time reducing cost, power
consumption, and complexity.
Because not all mobile telephone users require data capabilities,
one possible solution to the above mentioned disadvantages is to
offer two types of mobile telephones, a speech-only version and
a speech and data version. In so doing, the speech-only version
is not burdened with the added complexity, cost, and power consumption
needed to provide data capabilities. The purchaser of a voice only
mobile telephone who later desires to add data capabilities must
discard his speech-only telephone and purchase a speech and data
version, thereby wasting his initial capital investment.
SUMMARY OF THE INVENTION
The present invention eliminates these drawbacks.
The invention relates to a modular mobile telephone having two
separate modules: a speech-only module, and a data-only adaptor
module. A speech-only mobile telephone is achieved with the use
of the speech-only module, which comprises a fully functional mobile
telephone capable of transmitting and receiving signals to and from
the mobile telephone system. A speech and data mobile telephone
is achieved via the addition of a data module to the speech module.
The data adaptor module provides all the added circuitry required
for processing data signals. The radio telephone can be designed
so that the data module can be purchased separately and added on
to the speech-only telephone. The data module may be capable of
processing both data signals received from the mobile telephone
system and signals received directly from a data terminal.
In one embodiment, the adaptor has digital data encoding and multiplexing
circuits as well as decoding and demultiplexing circuits. It also
contains the additional memory necessary for digital operation.
This memory may be substituted or used in combination with the speech-only
memory. Further memory may be provided for connecting the data adaptor
module directly to a data terminal.
BRIEF DESCRIPTION OF THE DRAWING
The invention is described below referring to FIG. 1. FIG. 1 is
a block diagram of a mobile telephone according to the present invention.
The figure illustrates the principal functional blocks. A person
skilled in the art can realize the functional blocks with logic
circuitry in a variety of ways without undue experimentation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The functional blocks of a mobile telephone include a transmitter/receiver
(6) which receives "bursts" of information transmitted
from the mobile telephone system, and transmits information from
the mobile telephone to the mobile telephone system. Additionally,
the transmitter modulates and demodulates the transmitted and received
signals, respectively, according to the relevant modulation requirements
for the mobile telephone standard being implemented. For example,
if the standard being implemented were the Groupe Special Mobile
(GSM) standard of the Pan-European digital mobile telephone system,
the modulating technique employed would be Minimal Shift Keying
(MSK). Other mobile telephone standards, such as that for the U.S.
digital system, may also be used.
Further, in the transmit direction,the functional blocks of a mobile
telephone include a speech encoder (1), a channel encoder (2), and
a multiplexer (3). The speech encoder (1) converts input analog
speech signals into digital bits and compresses the digital bits
in order to remove redundant information and reduce the amount of
information that is required to be transmitted. The speech encoder
may be, for example, a pulse excited linear predictive coder with
a long-term prediction. The channel encoder (2) generates error
correction patterns that are added to the compressed digital bit
stream output from the speech encoder (1). The multiplexer (3) arranges
the compressed digital bits and the error correcting bits into appropriate
time slot information, which is then transmitted by the transmitter/receiver
(6) to the mobile telephone system in the appropriate speech time
slots according to the frame structure defined in the relevant digital
mobile telephone communication standard.
In the receive direction, the functional blocks of a mobile telephone
include a demultiplexer/channel decoder (4) and a speech decoder
(5). The demultiplexer/channel decoder (4) extracts the appropriate
speech time slot information from the received information from
the mobile telephone network, as well as stripping away the error
correction bits and performing any necessary error correction. The
speech decoder (5) expands the received compressed speech data and
converts it into analog form for further audio processing.
The architecture of the mobile telephone is implemented with a
microprocessor based central processing unit (CPU) (11) and a random
access memory (RAM) (12). The CPU (11) controls the other functional
blocks and stores information in the RAM (12). The size of the RAM
(12) is determined mainly by the frame format and data structure
of the particular digital mobile telephone standard being implemented.
Additionally, a small amount of memory is required for the control
and operation of the various functional blocks.
For example, if the standard being implemented were GSM, the RAM
(12) would be sized based on the particular parameters of the GSM
standard. In the GSM standard, each time slot contains 114 bits.
For a speech-only call, there are 8 time slots of speech information
and 4 time slots of control signal. Thus, each frame is (8+4)*114=1,368
bits. In addition, the mobile telephone must be capable of storing
4 frames of received information. Therefore, the required memory
for the receive function is 1,368*4=5,472 bits. In the transmit
direction, the transmitter need only be capable of storing 1 frame
of information or 1,368 bits. Thus, the total memory required for
the transmit/receive portion of a speech-only mobile telephone is
(5,472+1,368)=6,840 bits. These figures will vary for other mobile
telephone system standards.
In the case of a speech and data call, the time slots are still
114 bits. However, there are 8 time slots of speech information,
4 time slots of control signal, and 15 time slots of data information
per frame. Since the receiver portion must be capable of storing
4 received frames, the required receive memory will be (8+4+15)*114*4=12,312
bits. In the transmit direction, the transmitter only needs to store
1 frame of information which is (8+4+15)*114=3,078 bits. Thus, the
total memory required for the transmit/receive portion of a speech
and data mobile telephone is (12,312+3,078)=15,390 bits.
The modular approach of the present invention results in a circuit
arrangement for a speech-only mobile telephone that requires significantly
less memory than a speech and data version. For example, under the
GSM standard, a speech-only module requires less than half the memory
of a speech and data module (6,840 versus 15,390).
In order to facilitate the use of a modular design, the speech-only
module is provided with an interface (20), to which a data adaptor
or auxiliary terminal (30) can be connected. This interface (20)
may be a fast bus interface. The data adaptor (30) comprises substantially
similar functional blocks to those found in the speech-only module.
Specifically, the data adaptor (30) contains a channel encoder (2')
and a multiplexer (3') similar to channel encoder (2) and multiplexer
(3). Also, the data adaptor (30) contains a demultiplexer/channel
decoder (4') similar to demultiplexer/channel decoder (4).
The data adaptor (30) communicates with the CPU (11 ) via the interface
(20). In the GSM system, for example, the control signal received
by the CPU indicates whether the received signal contains voice
only or voice and data. The CPU (11 ) in accordance with the protocol
being implemented will disassemble received frames and route speech
information to the demultiplexer/channel decoder (4) and data information
to the demultiplexer/channel decoder (4') in the data adaptor. Likewise,
in assembling a frame to be transmitted the CPU (11) will route
speech information from the multiplexer (3) and data information
from multiplexer (3') to the transmitter portion of the transmitter/receiver
(6). The data adaptor may also be directly connected to a data terminal
(40) via a data terminal interface (50) to receive data-only signals
from a data source.
The additional RAM (32) in the data adaptor (30) will be used by
the CPU (11) either as either an additional RAM (12) or a replacement
for RAM (12). For example, in the case of the GSM standard, RAM
(12) may be about 7,000 bits for a speech-only configuration. In
the case of speech and data, RAM (32) may be used as a replacement
for RAM (12), in which case it would be about 16,000 bits in order
to satisfy the memory requirements for a speech and data mobile
telephone. Alternatively, it may be about 4,000 bits and used in
combination with RAM (12).
The mobile telephone can be arranged so that the data adaptor can
be added onto a speech-only phone. That is, a user can purchase
a speech-only phone and later purchase the data adaptor, which will
plug into an interface constructed in the speech-only mobile phone.
While the present invention has been particularly shown and described
with reference to preferred embodiments thereof, it is understood
by those skilled in the art that various changes in the form and
details may be made therein without departing from the spirit and
scope of the invention.
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