Patent Application
20090221324
Embodiments of the invention relate to a combined global navigation satellite system (GNSS) receiver and cellular system receiver. More specifically embodiments of the invention relate to a receiver in which the radio path between GNSS and cellular system signals can be shared. Embodiments of the invention also relate to a corresponding method, system, module and computer program product.
In cellular systems, different multiple access techniques can be applied depending on the cellular system standard. In the global system for mobile communications (GSM), combined time and frequency division multiple access techniques are applied (TDMA/FDMA). The FDMA technique involves the division of the 25 MHz bandwidth into 124 carrier frequencies spaced 200 kHz apart. Several carrier frequencies can be assigned to each base station (BS). According to the TDMA technique, these carrier frequencies are then divided in the time domain. The fundamental time unit in this TDMA technique is called a burst period (or time slot) and it lasts 15/26 ms (or approximately 0.577 ms). Eight burst periods or time slots are grouped into a TDMA frame ( 120/26 ms, or approximately 4.615 ms), which forms the basic unit for the definition of logical channels. One physical channel is defined to be one burst period per TDMA frame.
Minimising interference in the network is a goal in any cellular system, since it allows better service for a given cell size, or the use of smaller cells, thus increasing the overall capacity of the system. Discontinuous transmission (DTX) aims at increasing the system efficiency through a decrease of the interference level by inhibiting the transmission of the radio signal when not required from an information point of view. DTX takes advantage of the fact that a person speaks less than 40 percent of the time in normal conversation. An added benefit of DTX is that power is conserved at the mobile unit. DTX is also called variable bit rate since in the DTX mode the transmitted bit rate is less than in a situation in which a person is speaking.
The most important component of DTX is voice activity detector (VAD). It must distinguish between noise and voice inputs. When the transmitter is turned off, there is total silence heard at the receiver. To assure the receiving end that the connection is not dead, comfort noise is created at the receiver to match the transmitting end's background noise characteristics. For instance in GSM, the noise characteristics are transported to the receiving end by specific frames called silence descriptor (SID) frames. A SID frame is sent at the beginning of every inactivity period, and more are then sent regularly, at least twice a second, as long as the inactivity lasts. Therefore, the receiving end can generate comfort noise based on the received SID frame. DTX can be used also in systems employing code division multiple access (CDMA) technique. An example of such a cellular system is for instance universal mobile telecommunication system (UMTS), which employs wideband CDMA.
Currently GNSS receivers are being integrated into cellular system terminals.
U.S. Pat. No. 6,831,911 by Ashvattha Semiconductor Inc relates generally to a system and method for receiving and processing global positioning system (GPS) and wireless phone signals using a combination receiver, more particularly, receiving and processing GPS signals and wireless signals during alternate time segments by suspending reception of GPS signals during times when wireless signal is received. In the event that the user desires to place or receive a wireless phone call, using a time division technology wireless phone, the receiver will suspend reception of GPS signal to receive or transmit the wireless phone signal. Therefore, it becomes possible to combine a GPS receiver and a wireless phone using a single integrated circuit because either the GPS receiver or the wireless phone is operating, but not both at the same time. A TDMA wireless phone signal can be received and processed in time segments alternating with a GPS signal. The TDMA data is sent in signal bursts that last a predetermined length of time in accordance with the particular time division standard. Therefore, the GPS receiver can be turned on to receive a GPS signal, then turned off to receive a TDMA signal. When the TDMA signal has been received, the receiver can be switched to the GPS operational mode again.
The applicant has recognised that there is a need to share the RF section part of the receiver between the cellular and GNSS signals based on the detected voice activity of the transmitter.
According to a first aspect of the invention, there is provided a method for a first wireless communication device to operate in wireless communication system mode and satellite positioning system mode, wherein in the satellite positioning system mode the first wireless communication device receives signals from the satellite positioning system and in the communication system mode it receives signals from the communication system, the method comprising the first wireless communication device: communicating with a second communication device; determining voice activity of at least one of the communication devices; based on the determined voice activity, switching between the wireless communication system mode and the satellite positioning system mode.
The invention has in accordance with one embodiment the advantage that it provides a way to optimise the performance of the communication device with minimal speech quality degradation. The invention makes it possible to switch between satellite system signal reception and communication system signal reception.
Further, according to a first aspect of the invention the wireless communication device is a mobile phone handset.
Other aspects of the invention are in the claims appended hereto.
These and other features of the present invention will by way of example become apparent from the following detailed description when considered in conjunction with the accompanying drawings, in which:
The mobile phone handsets 310, 350 communicate with each other via the communication network comprising the BS 320 and the MSC 330. The BS 320 communicates with the mobile phone handsets 310, 350 using RF transmissions or any other suitable communication means in order to transmit signals to the mobile phone handsets 310, 350. Accordingly, the mobile phone handsets 310, 350 receive transmissions sent by the BS 320. The mobile phone handsets 310, 350 also send signals to the BS 320. Thus, the communication is two directional. BSs and MSCs form part of the cellular communications network, such as a GSM network. In this particular exemplary embodiment the mobile phone handsets 310, 350 are communicating with each other and the handset 310 is also able to receive signals from at least one of the satellites 340. The satellites 340 transmit signals to the mobile phone handsets 310, 350 either directly, without intervention of the communication network or via the cellular communication network so that the communication network can send assistance data to the mobile phone handsets 310, 350. Wireless communication link is used for signal transmissions from the satellites 340 to the handsets 310, 350 and to the BS 320. In the communication network, the satellite signals are received by a location measurement unit (LMU), which may be physically located in the same place as the BS 320. If however, the LMU is located in the different place than the BS 320, the signal needs to be conveyed to the BS 320 so that the BS 320 can then send it to the mobile phone handsets 310, 350. The signals received from the satellites 340 can also be processed before they are sent to the mobile phone handsets 310, 350 as assistance data.
The handset 310 also includes a cellular engine 406 for providing communication capabilities with the cellular communication network, such as GSM network. For receiving and processing the satellite transmissions, the handset comprises a positioning engine (pos engine) 407. The handset 310 also includes transceiver unit 402 (TRX). For receiving and transmitting signals, the handset 310 includes an antenna 401. Two or more physically separated antennas could also be used, but in this embodiment the cellular and satellite system antennas are combined into a single physical antenna which can receive and transmit signals of the cellular system and receive signals of the satellite system.
The handset 310 also includes a central processing unit 403 (CPU) for centrally controlling the functioning of the handset 310. The CPU includes one or more processing units depending on the implementation of the handset 310. For detecting voice activity, the handset 310 comprises a VAD 404 and for detecting the comfort noise received by the antenna 401, the handset 310 comprises a comfort noise detector (CND) 409.
If there is no need for dual mode signal reception, then at step 505 either one of these signals can be received at a time or there may not be a need for any signal reception. If however at step 501 it is determined that there is a need for dual mode signal reception, then at step 502, voice activity of the transmitting handset 350 is determined. At step 503 signal reception is switched between cellular and satellite system reception depending on the transmitting handset 350 voice activity determined in step 502. If the transmitting handset 350 is silent, then the RF section of the receiving handset 310 can be predominantly used for reception of satellite signals. If it is determined that the transmitting handset 350 is not silent, then the RF section of the receiver can be predominantly used for reception of cellular system signals. At step 504 it is again determined whether there is a need for dual mode reception of signals from the satellites 340 and from the cellular system. If there is a need for dual mode signal reception then the voice activity is again determined at step 502. If there is no need for dual mode signal reception then at step 505 either satellite or cellular system signals can be received at a time or there may not be a need for any signal reception.
After the selector 606 the signal is led into the RF section part where the signal is divided into two different branches. These two branches comprise same components and the difference in these two branches is that the signal has in the other branch 90 degrees phase offset due to the phase offset block 608. After the selector 606 the signal is mixed with the local oscillator 609 signal and for the signal in the other branch a 90 degrees phase offset is introduced. After the mixer 610, there is a low pass filter (LPF) 611 for filtering out high frequencies. After the LPF 611, the signal is amplified by variable gain amplifier (VGA) 612 and finally the analogue signal is converted to digital form by the analogue-to-digital (A/D) converter 613. The signal is then led to digital base band part of the receiver.
The operation of the handset 310 of
However, if it is determined at step 501 that there is a need for dual mode signal reception from both the transmitting handset 350 and from the satellites 340, then at step 502 voice activity of the transmitting handset 350 is determined. This can be done by the receiving handset 310 detecting data frames sent by the transmitting handset 350. If it is detected that the transmitting handset 350 has sent a specific frame, for instance a SID frame, indicating that the transmitting handset 350 is inactive, then the receiving handset 310 can determine that the transmitting handset 350 is not speaking, i.e. it is inactive. The transmitting handset 350 can also send comfort noise to the receiving handset 310. In this case, if the VAD 404 of the handset 350 detects that the user of the handset 350 is not active, the comfort noise is sent at a lower bit rate than speech would be sent. This reduces load in the communication network. There can also be a VAD in the receiving handset 310 and when it is detected that the receiving handset 310 is silent then it can be predicted that the transmitting handset 350 is speaking. Or alternatively when it is detected that the receiving handset 310 is speaking then it can be predicted that the transmitting handset 350 is silent.
Then at step, 503 the selector 606 of
At step 504 it is again checked whether dual mode signal reception from the transmitting handset 350 and from the satellites 340 is still needed. If this is the case then again at step 502 the voice activity of the transmitting handset 350 is determined. If however there is no need for dual mode signal reception, then at step 505 just signals from the satellites 340 or from the transmitting handset 350 can be received at a time.
At step 703 the receiving handset 310 functions in transmitting handset active mode. In transmitting handset active mode the GNSS reception part is active, for instance, 100 ms in a second. In this case cellular system signal reception would be active a majority of the time, for instance 900 ms in a second. This is illustrated in
Then at step 704 the receiving handset 310 determines whether dual mode reception is needed. If there is no need for dual mode reception, then at step 709 the dual mode reception can be terminated. If however dual mode reception is needed, then at step 705 it is determined whether the transmitting handset 350 is active or not. This can be done by the receiving handset 310 decoding data frames sent by the transmitting handset 350 during cellular system mode. If a SID frame is detected then the receiving handset 310 can determine that the user of the transmitting handset 350 is inactive. If however speech frames are received by the receiving handset 310, then it can be determined that the user of the transmitting handset 350 is speaking and is therefore active. The VAD 404 is needed in the transmitting handset 350 to detect whether the user of the transmitting handset 350 is active or not. If the user is not active, then data can be sent to the receiving handset 310 at a lower bit rate then speech would be sent. If the user of the transmitting handset 350 is active, then at step 703 transmitting handset active mode is used.
If the receiving handset 310 determines that the transmitting handset 350 is not active then at step 706 transmitting handset silent mode is used. In transmitting handset silent mode the GNSS reception part is active, for instance, 900 ms in a second. In this case cellular system signal reception would be active minority of the time, for instance 100 ms in a second. This is illustrated in
At step 707 it is again determined whether there is a need for dual mode signal reception. If there is no need for dual mode reception, then at step 709 the dual mode reception can be terminated. If dual mode reception is still needed then the receiving handset 310 determines at step 708 whether the transmitting handset 350 is active or not. If the transmitting handset 350 is not active, then at step 706 transmitting handset silent mode is used. If however the transmitting handset 350 is active, then at step 703 transmitting handset active mode is used.
At step 1003 the receiving handset 310 functions in transmitting handset active mode. In transmitting handset active mode the GNSS reception part is active for instance 100 ms in a second. In this case cellular reception would be active majority of the time, for instance 900 ms in every second. Also other suitable active periods for the different reception parts can be used.
Then at step 1004 it is determined whether dual mode reception is needed. If there is no need for dual mode reception, then at step 1012 the dual mode reception can be terminated. If however the dual mode reception is needed, then at step 1005 the receiving handset 310 determines whether the transmitting handset 350 is active, i.e. the user of the transmitting handset 350 is speaking. If the transmitting handset 350 is active, then at step 1003 transmitting handset active mode is used. For detecting voice activity, the same methods can be employed as explained previously. Since in this embodiment, the VAD 404 is also in the receiving handset 310, it can be used for predicting voice activity of the user of the transmitting handset 350. If it is detected that the user of the receiving handset 310 is silent then it can be predicted that the user of the transmitting handset 350 is speaking. Or alternatively when it is detected that the user of the receiving handset 310 is speaking then it can be predicted that the user of the transmitting handset 350 is silent. If it is determined that the transmitting handset 350 is not active then at step 1006 the receiving handset 310 uses both end silent mode. In both end silent mode the cellular system reception part can be active for instance 500 ms in a second whereas the satellite reception part can be active equal time period. This is illustrated in
Then at step 1007 the receiving handset 310 determines whether dual mode reception is still needed. If there is no need for dual mode reception, then at step 1012 the dual mode reception can be terminated. If however the dual mode reception is needed, then at step 1008 it is determined whether the user of the transmitting handset 350 is active. If it is determined that the user of the transmitting handset 350 is active then at step 1003 transmitting handset active mode is used. If the user of the transmitting handset 350 is not active then at step 1009 the receiving handset 310 determines whether the user of the receiving handset 310 is active or not. This can be determined by using the VAD 404 in the receiving handset 310. If the user of the receiving handset 310 is active, then at step 1010 receiving handset active mode is used. In this mode the GNSS reception could be active for instance 900 ms in a second whereas the cellular reception part could be active the remaining time, i.e. 100 ms in a second. If at step 1009 the receiving handset 310 determines that the user of the receiving handset 310 is not active, then at step 1006 both end silent mode is used.
Then at step 1011 the receiving handset 310 again determines whether dual mode signal reception is needed. If there is no need for dual mode reception, then at step 1012 the dual mode reception can be terminated. If however the dual mode reception is needed, then at step 1013 the receiving handset 310 determines whether the user of the transmitting handset 350 is active. If the receiving handset 310 determines that the user of the transmitting handset 350 is active then at step 1003 transmitting handset active mode is used. If the user of the transmitting handset 350 is not active then at step 1014 the receiving handset 310 determines whether the user of the receiving handset 310 is active. If the receiving handset 310 determines that the user of the receiving handset 310 is active then at step 1010 the receiving handset active mode is used. If the user of the receiving handset 310 is not active, then at step 1006 both end silent mode is used.
The invention also relates to a corresponding computer program product, which can be used to implement at least some parts of the method according to the embodiments described above.
In the receiving handset 310 all inventive features could be incorporated into a single module. The module should at least include the selector switch and in some embodiments also the VAD 404 and/or CND 409.
The invention also relates to the receiving handset 310 and transmitting handset 350, which comprise means for implementing the methods described above. The receiving handset 310 and transmitting handset 350 may also comprise the module described above.
Furthermore the invention relates to a system in which the receiving handset 310 can be used. The system comprises at least the receiving handset 310 and transmitting handset 350 and at least one satellite 340.
It is to be noted that the described embodiments can be varied in many ways and that these are just exemplary embodiments of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0525096.4 | Dec 2005 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2006/004035 | 12/8/2006 | WO | 00 | 3/23/2009 |
