AU711184B2 - Method for realizing frequency hopping and a base station equipment - Google Patents
Method for realizing frequency hopping and a base station equipment Download PDFInfo
- Publication number
- AU711184B2 AU711184B2 AU59361/98A AU5936198A AU711184B2 AU 711184 B2 AU711184 B2 AU 711184B2 AU 59361/98 A AU59361/98 A AU 59361/98A AU 5936198 A AU5936198 A AU 5936198A AU 711184 B2 AU711184 B2 AU 711184B2
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- AU
- Australia
- Prior art keywords
- signal
- base station
- equipment
- frequency
- carrier frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/08—Access point devices
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/12—Frequency diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2643—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA]
- H04B7/265—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile using time-division multiple access [TDMA] for channel frequency control
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W48/00—Access restriction; Network selection; Access point selection
- H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
- H04W48/12—Access restriction or access information delivery, e.g. discovery data delivery using downlink control channel
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
Description
S F Ref: 319062D1
AUSTRALIA
PATENTS ACT 1990 COMPLETE SPECIFCATION FOR A STANDARD PATENT
ORIGINAL
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Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Nokia Telecommunications OY Makkylan puistotle 1 FIN-02600 Espoo
FINLAND
Eero Heikkinen Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Method for Realizing Frequency Hopping and a Base Station Equipment The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845
I
ooooo 15 20 25 .2 1 Method for realizing frequency hopping and a base station equipment The present invention relates to a method for implementing frequency hopping in a base station of a digital cellular radio system, in which base station a first signal modulated by base band data signal is transmitted on a certain carrier frequency, which signal is divided in the time domain into several time slots of which one time slot transmits the common control channel of the base station equipment and the other time slots information regarding different connections.
In cellular radio systems, the quality of a radio channel varies as a function of time and place.
On many occasions a transmitting antenna and a receiving antenna are not within sight of each other due to obstacles formed by terrain or buildings in the line of sight, and thus the signal detected at the receiver is a sum of beams that have travelled different paths and have been reflected from obstacles and that are, further, with different phases. The sum of several signals with different phases follows the Rayleigh distribution in cases of randomly distributed phases.
Signal fading is, furthermore, dependent on the frequency of the signal. Thus, if a frequency difference between two signals is great enough, their fadings do not corrclatc. A1 diffsrence oL 1 MHz, L tix upie, is large enough for signal fadings to be independent of each other.
The frequency selective fading of a signal described above is one reason for the introduction of frequency hopping technology in digital cellular radio networks. Frequency hopping means that the transmission frequency used in a connection is changed at predetermined intervals. Due to frequency hopping, the transmission quality can be improved especially in situations in which the terminal equipment moves very slowly or not at all as is often the case with, for example, handheld phones.
Apart from the frequency diversity achieved by frequency hopping, the method is also advantageous in distributing the interference caused by the radio connection onto several frequencies, in which case momentary interference on any one frequency will remain small.
In the prior art solutions, if frequency hopping has been desired in a cell served by a base station, the base station equipment must have been provided with at least two complete transceiver units which contain base band sections and radio frequency sections. Each unit as such can form an independent base station, but to implement frequency hopping several of them have been required in the same cell.
This has resulted in that the base station equipment capable of frequency hopping has been disproportionately large in small cells in comparison with the capacity needed, and S. 15 the implementation of frequency hopping has thus required heavy investments.
a ba s It is thus an object of the present invention to implement frequency hopping in a base station equipment economically and without creating excessive capacity.
Therefore, the invention discloses a base station equipment in a digital cellular S. radio system, said equipment comprising means for generating a base band data signal, 20 a first means for transmitting a signal modulated by a certain first carrier frequency, said transmitted signal being divided in the time domain into several time slots of which one transmits the common control channel of the base station equipment and the other time slots transmit information regarding different connections, and an antenna, wherein the equipment further comprises: 25 a second means for transmitting a signal modulated by a second carrier frequency, Plempntc for phagingr th, -ond ie-A III -d in te ud ans time-slot-specifically so that successive time slots may be transmitted using a different second carrier frequency, and [N:\Iibk]00660:MXL -3means for distributing the base band signal to the first and the second transmitting means so that the signal transmitted by the second means is divided in the time domain into several time slots of which each transmits the same information as the signal transmitted by the first means except the time slot that transmits the common control channel of the base station equipment.
The invention further discloses a method for implementing frequency hopping in a base station of a digital cellular radio system, in which base station in regard to a first signal the method comprising the steps of: modulating a first signal by a base band data signal; transmitting said first signal on a first carrier frequency, which signal is divided in the time domain into several time slots of which one time slot transmits the common control channel of the base station equipment and the other time slots transmit information regarding different connections; -the base station further transmits a second signal and in regard to said second 15 signal the method further comprises the steps of: modulating said second signal by the same base band data signal on a certain second carrier frequency, and dividing said second signal in the time domain into several time slots, each of which transmits the same information as the first signal, except the time slot which 20 transmits the common control channel of the base band equipment, and which second carrier frequency is changed time-slot-specifically so that successive time slots may be transmitted using a different second carrier frequency so that the frequency is either the same as the first carrier frequency or different than that.
The method of the invention can be applied for implementing frequency 25 hopping in a cell comprising one transceiver unit. The base station in accordance with the invention can be built similarly to a conventional non-hopping base station, the only [N:\libk]00660:MXL -4necessary changes being in the RF section of the transmitter. Only one base band section is needed. If frequency hopping is unnecessary, the base station of the invention can easily implement space diversity in a direction from the base station to the mobile station. The use of frequencies can be optimized so that frequency hopping is utilized only on weak connections.
In the following, embodiments of the invention will be described in greater detail with reference to the examples in accordance with the accompanying drawings, in which Figure 1 illustrates time-slot-specific frequency hopping, Figure 2 shows an example of the structure of a base station equipment in accordance with an embodiment of the invention, Figure 3 shows another example of the structure of a base station equipment in accordance with an embodiment of the invention, and Figures 4a-4b describe the time slot construction of the output signal of the transmitting means.
The invention can thus be applied in the base station equipment of digital cellular radio systems such as the GSM system, for instance. In the following, an embodiment of the invention will be described when applied in a time slot structure of type used in the GSM system, but without being restricted to that.
S 20 Figure 1 illustrates the implementation of time-slot-specific frequency hopping.
The horizontal axis of the figure represents time, and the vertical axis represents frequency. The figure shows the frequency changes of one channel according to time slots. The base station changes carrier frequency at the beginning of every time slot, but the frequency is not changed during the time slot. The frequency is changed S. 25 according to a predetermined sequence, in which case the receiver can monitor the hopping and receive the information contained in each time slot on a correct frequency.
In a hve. .tntinn inoh rnnnrt;nn oan hxr [N:\libk]00660:MXL a hop sequence of its own, in which case the frequencies used in the time slots do not overlap.
Figure 2 is a block diagram of the structure of a base station equipment in which the method of the embodiment is applied. The equipment contains means for generating a base band signal. The output 16 of said means 15 is connected to two transmitter units 10,18 with the aid of a base band signal divider. The first transmitter unit 10 contains a carrier generator 12 whose output 26 is connected to a modulating means 13 whose second input is a base band data signal from the base band signal divider 17. The time division carrier signal 23 modulated by a base band signal is fed via an output amplifier 14 to an antenna 11. The first signal 15 of the transmitter unit contains the common control channel BCCH of a cell served by a base station. By listening to that signal, mobile stations obtain information of the base station so that they can contact it, if necessary. In a GSM system, traffic on the BCCH channel is transmitted in the first time slot of a frame, indicated by the number 0. The other time slots, of which there are seven in a GSM system, transmit a signal that is either data belonging to a connection or, if the time slot is not in use, is a dummy burst. Figure 4a illustrates the structure of a GSM frame in which the first time slot 0 contains the BCCH channel, the second time sln-c- 1 dmm .hIn SIo 2, 3, 4 ana b data information, and time slots 5 and 7 a dummy burst. The carrier frequency of the transmitter 10 is marked with fl, and it is constant.
The second transmitter unit 18 correspondingly contains a carrier generator 20 whose output 27 is connected to modulation means 21 whose second input is the base band data signal from the base band signal divider- 17, i.e. the same signal as in the input of the 6 first transmitter unit. In the example of the figure, the time division carrier signal 24 modulated by the base band signal is supplied via output amplifier 22 to an antenna 19. The signal of the second transmitter unit does not contain the common control channel BCCH, and the said time slot is not transmitted. In the other time slots 1-7 data belonging to some connection is transmitted, or the transmitter is switched off, if the time slot is not in use.
The carrier frequency used by the second transmitter unit hops time-slot-specifically under the control of means 25 so that with each connection (i.e.
time slot) the frequency changes according to a S. predetermined sequence. In a base station in accordance 15 with figure 2, in which two antennas are in use, the carrier frequency of the second transmitter unit can momentarily be the same as the frequency fl used by the first transmitter unit.
'0 According to a second embodiment, when both of 20 the transmitter units are on the same frequency, the second transmitter unit is switched off to avoid simultaneous transmission.
The second transmitter unit can be controlled time-slot-specifically so that frequency hopping is only performed in certain time slots. If two antennas are in Suse in connections not applying frequency hooDing h-th transmitters transmit the same signal on the same frequency, and space diversity is obtained.
Frequency use can be optimized so that frequency hopping is only applied to poor quality connections. To judge communication quality, signal Strength as well as bit error and signal-to-noise ratios can be used as standards.
Figure 3 is a block diagram representation of an alternative structure of a base station equipment realizing the method of the embodiment. The equipment contains means 30 for combining signals from two transmitter units 10, 18 for transmitting via one antenna 11. The operation of a base station sach as the one in figure 3 is similar to the above except that when one antenna is used, the second transmitter unit is switched off in cases where its carrier frequency is the same as the frequency of the first transmitter unit.
In addition to the components described above, the exemplary base stations also contain components other than those described, such as filters and divider amplifiers, but due to reasons of clarity they have been omitted from the figure as they are not essential to the present embodinent.
15 5 As explained above, figure 4a illustrates a Sframe structure transmitted by the first transmitter unit, first containing i the istime slot 0 containing the BCCH channel, time slots 2, 3, 4 and 6 containing data information (Cl-C4), and time slots 1, 5 and 7 containing a dummy 20 burst (Bl-B3). The carrier frequency of the first Stransmitter is indicated by fl, and it is constant.
Figure 4b illustrates a frame structure transmitted by the second transmitter unit. In the example illustrated in the figure the transmitter unit 25 utilizes three different frequencies, f2, f3 and f4 in frequency hopping. The number of frequencies can, of course, be somethino els n et us assume -that connections Cl C2 Le t us assume that connections Cl, C2 and C4 using time slots 2, 3 and 6 employ frequency hopping, but connection C3 using time slot 4 does not hop. In such a case the second transmitter unit transmits a signal in time slots 2, 3 and fs a signal in time slots 2 3 and 6 as shown by the figure, using at each 2 oment of time one of the said carrier frequencies f-f4. The second transmitter unit can, depending on the application, also use the frequency fl of the first 8 transmitter unit. The frequency used at each connection and each moment of time depends on the chosen hopping sequence which is specific for each connection.
The second transmitter unit can, for example, transmit a frame in accordance with figure 4b so that time slot 2 uses frequency f2, time slot 3 frequency f3 and time slot 6 frequency f4. In the next frame the time slots are changed so that time slot 2 uses frequency f3, time slot 3 frequency f4 and time slot 6 frequency f3.
The frequencies of the time slots are independent of each other, and they can also be the same.
When two separate antennas are used, the second transmitter unit is able to transmit on non-hopping connections the time slot in question on the same space diversity is achieved at the transmitting end. In *the example above, the second transmitter unit can thus transmit the signal of connection C4 in time slot 4 on a frequency fl.
20 Even when using two separate antennas the second transmitter unit can be switched off if the frequencies of the transmitter units are the same; this can de done to avoid simultaneous transmission.
Even though the invention has been described in the above with reference to the examples in accordance with the accompanying drawings, it is obvlou that the invention is not restricted to them but can be modified in a variety of ways.
Claims (14)
1. A base station equipment in a digital cellular radio system, said equipment comprising means for generating a base band data signal, a first means for transmitting a signal modulated by a certain first carrier frequency, said transmitted signal being divided in the time domain into several time slots of which one transmits the common control channel of the base station equipment and the other time slots transmit information regarding different connections, and an antenna, wherein the 10 equipment further comprises: a second means for transmitting a signal modulated by a second carrier S" frequency, elements for changing the second carrier frequency used in the second means time-slot-specifically so that successive time slots may be transmitted using a different 15 second carrier frequency, and means for distributing the base band signal to the first and the second transmitting means so that the signal transmitted by the second means is divided in the time domain into several time slots of which each transmits the same information as the signal transmitted by the first means except the time slot that transmits the common 20 control channel of the base station equipment.
2. An equipment as claimed in claim 1 wherein the first and the second means comprise: means for generating a first and second carrier wave, means for modulating the first and second carrier wave by a base band signal, and an amplifying means for the modulated signal. [N:\libk]00660:MXL
3. An equipment as claimed in claim 1, wherein the equipment comprises a second antenna which is connected to the amplifying means.
4. An equipment as claimed in claim 1, wherein the equipment comprises means for combining signals from two transmitters to be transmitted via one antenna.
An equipment as claimed in claim 1, wherein elements change the second carrier frequency employed by the second means according to a predetermined sequence. oO"
6. An equipment as claimed in claims 4 and 5, wherein the elements ~switch off the second means when the frequency indicated by the sequence is the same as the frequency used by the first means. 15
7. A method for implementing frequency hopping in a base station of a digital cellular radio system, in which base station in regard to a first signal the method comprising the steps of: modulating a first signal by a base band data signal; transmitting said first signal on a first carrier frequency, which signal is divided in the time domain into several time slots of which one time slot transmits the common control channel of the base station equipment and the other time slots transmit information regarding different connections; the base station further transmits a second signal and in regard to said second signal the method further comprises the steps of: modulating said second signal by the same base band data signal on a certain second carrier frequency, and dividing said second signal in the time domain into several time slots, each of which transmits the same information as the first signal, except the time slot which [N:\Iibki00660:MXL A -11- transmits the common control channel of the base band equipment, and which second carrier frequency is changed time-slot-specifically so that successive time slots may be transmitted using a different second carrier frequency so that the frequency is either the same as the first carrier frequency or different than that.
8. A method as claimed in claim 7, whereby the carrier frequency is changed time-slot-specifically following a predetermined sequence.
9. A method as claimed in claim 7, whereby both the first and the second 10 signal are transmitted via their own respective antennas. 4*
10. A method as claimed in claim 7, whereby both the first and second signal are transmitted via the same antenna. 15
11. A method as claimed in claims 7 and 10, whereby if the carrier frequency indicated by the sequence and used by the second signal is the same in each atime slot as the carrier frequency used by the first signal, the second signal is not transmitted.
12. A method as claimed in claim 7, whereby the second signal is transmitted time-slot-specifically when the quality of the signal transmitted in the time slot at the receiving end is poorer than a predetermined threshold value.
13. A base station equipment substantially as herein described with reference to the accompanying drawings. [N:\libk]00660:MXL -12-
14. A method for implementing frequency hopping in a base station substantially as herein described with reference to the accompanying drawings. DATED this Tenth Day of March 1998 Nokia Telecommunications OY Patent Attorneys for the Applicant SPRUSON FERGUSON 60990: 6 a 0 06%." [N:\HibkIOO66O: MXL
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU59361/98A AU711184B2 (en) | 1994-03-18 | 1998-03-18 | Method for realizing frequency hopping and a base station equipment |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI941289A FI941289A (en) | 1994-03-18 | 1994-03-18 | Method for realizing frequency jumping and a base station device |
| FI941289 | 1994-03-18 | ||
| AU19520/95A AU688878B2 (en) | 1994-03-18 | 1995-03-16 | Method for realizing frequency hopping and a base station equipment |
| AU59361/98A AU711184B2 (en) | 1994-03-18 | 1998-03-18 | Method for realizing frequency hopping and a base station equipment |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU19520/95A Division AU688878B2 (en) | 1994-03-18 | 1995-03-16 | Method for realizing frequency hopping and a base station equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU5936198A AU5936198A (en) | 1998-05-21 |
| AU711184B2 true AU711184B2 (en) | 1999-10-07 |
Family
ID=25617550
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU59361/98A Ceased AU711184B2 (en) | 1994-03-18 | 1998-03-18 | Method for realizing frequency hopping and a base station equipment |
Country Status (1)
| Country | Link |
|---|---|
| AU (1) | AU711184B2 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991012681A1 (en) * | 1990-02-06 | 1991-08-22 | Motorola, Inc. | Interconnecting and processing system for facilitating frequency hopping |
| WO1993017507A1 (en) * | 1992-02-28 | 1993-09-02 | Telefonaktiebolaget Lm Ericsson | A method for communication in a tdma cellular mobile radio system using frequency hopping |
| WO1993020625A1 (en) * | 1992-03-27 | 1993-10-14 | Telefonaktiebolaget Lm Ericsson | A base station for a frequency hopping tdma radio communication system |
-
1998
- 1998-03-18 AU AU59361/98A patent/AU711184B2/en not_active Ceased
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991012681A1 (en) * | 1990-02-06 | 1991-08-22 | Motorola, Inc. | Interconnecting and processing system for facilitating frequency hopping |
| WO1993017507A1 (en) * | 1992-02-28 | 1993-09-02 | Telefonaktiebolaget Lm Ericsson | A method for communication in a tdma cellular mobile radio system using frequency hopping |
| WO1993020625A1 (en) * | 1992-03-27 | 1993-10-14 | Telefonaktiebolaget Lm Ericsson | A base station for a frequency hopping tdma radio communication system |
Also Published As
| Publication number | Publication date |
|---|---|
| AU5936198A (en) | 1998-05-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |