SE464553B - METHOD OF SYNCHRONIZATION IN A MOBILE RADIO SYSTEM - Google Patents
METHOD OF SYNCHRONIZATION IN A MOBILE RADIO SYSTEMInfo
- Publication number
- SE464553B SE464553B SE8902994A SE8902994A SE464553B SE 464553 B SE464553 B SE 464553B SE 8902994 A SE8902994 A SE 8902994A SE 8902994 A SE8902994 A SE 8902994A SE 464553 B SE464553 B SE 464553B
- Authority
- SE
- Sweden
- Prior art keywords
- base station
- time
- messages
- signaling
- mobile
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/12—Transmitting and receiving encryption devices synchronised or initially set up in a particular manner
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
- H04W12/03—Protecting confidentiality, e.g. by encryption
- H04W12/037—Protecting confidentiality, e.g. by encryption of the control plane, e.g. signalling traffic
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
- H04L2209/80—Wireless
Landscapes
- Engineering & Computer Science (AREA)
- Computer Security & Cryptography (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Time-Division Multiplex Systems (AREA)
Description
i4e4 555 10 15 20 25 2 någon anledning bortfaller. Vid överföring (hand-off) av ett samtal från en radiokanal till en annan radiokanal kan synkroniseringen mellan mobilen och dess basstation gå förlorad, eftersom ett kortvarigt avbrott under själva överföringen uppträder. Om samtalet dessutom är krypterat kan ytterligare problem uppstå genom att synkronismen för själva krypteringsnyckeln bort- faller, varvid dekrypteringen blir omöjlig. i4e4 555 10 15 20 25 2 any reason lapses. During the transfer (hand-off) of a call from one radio channel to another radio channel, the synchronization between the mobile and its base station may be lost, as a short-term interruption occurs during the transmission itself. In addition, if the call is encrypted, further problems may arise as the synchronization of the encryption key itself is lost, making decryption impossible.
Ovanstående problem förekommer även vid uppkoppling av krypterade samtal, men är mest påtagliga vid "hand-off".The above problems also occur when connecting encrypted calls, but are most obvious when "hand-off".
Föreliggande uppfinning grundar sig på tidsuppdelningen i olika ramar av trafikflödet (TDMA-principen) och att man har tillgång till en viss krypterings- sekvens som varar under en relativt lång tid (ca 3 minuter) relativt den tid under vilken uppkoppling eller "hand-off" skall ske. Vidare bygger uppfinningen på att krypteringen görs medelst överlagring av en bitsekvens på det normala trafikflödet (data eller tal jämte signalering). Före uppkoppling av ett samtal eller under ett visst tidsintervall vid "hand-off" då synkroniseringen av kryp- teringssekvensen bortfallit utförs först en okrypterad signalering och därefter en kryptering av trafikflödet med en periodisk bitsekvens, vars period är lika med ett ramtidsintervall. Härigenom kan man överföra synkroniseringsinforma- tion till en mobil från en basstation samtidigt med ett krypterat trafikflöde och som anger när den normala krypteringen skall påbörjas. Ändamålet med föreliggande uppfinning är således att i ett mobiltelefonsystem, som saknar gemensam tidsreferens åstadkomma synkronisering av en kryptosek- vens vid uppkoppling eller överkoppling ("hand-off") av samtal.The present invention is based on the time division into different frames of the traffic flow (TDMA principle) and that one has access to a certain encryption sequence that lasts for a relatively long time (about 3 minutes) relative to the time during which connection or "hand-off" " shall be done. Furthermore, the invention is based on the encryption being done by superimposing a bit sequence on the normal traffic flow (data or speech along with signaling). Before connecting a call or during a certain time interval at "hand-off" when the synchronization of the encryption sequence has failed, first an unencrypted signaling is performed and then an encryption of the traffic flow with a periodic bit sequence, the period of which is equal to a frame time interval. In this way, synchronization information can be transmitted to a mobile from a base station at the same time as an encrypted traffic flow and which indicates when the normal encryption is to be started. The object of the present invention is thus to provide, in a mobile telephone system which does not have a common time reference, synchronization of a crypto sequence during connection or hand-off of calls.
Uppfinningen är kännetecknad enligt vad som framgår av efterföljande patent- krav.The invention is characterized according to what appears from the following patent claims.
FIGURBESKRIVNIPB Uppfinningen skall närmare beskrivas med hänvisning till bifogade ritning(-ar) där figur l visar schematiskt två basstationer och en mobilenhet; figur 2 visar ett tidsschema för sändning och mottagning enligt TDMA- principen; 10 15 20 25 n 464 ' 553 3 figur 3 visar ett tidsdiagram för kryptering enligt den föreslagna metoden; figur 4 visar närmare signalering under ett visst tidsintervall enligt figur 3; UTFÖRINBSFORMER Figur l visar schematiskt tva basstationer B51 och B82 och en mobil MS som antas förflytta sig från basstationen BSl mot basstationen BS2. Basstationen BSl betjänar trafik inom cellen Cl och basstationen B52 trafik inom cellen CZ.DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawing (s), in which Figure 1 schematically shows two base stations and a mobile unit; Figure 2 shows a time schedule for transmission and reception according to the TDMA principle; Figure 3 shows a time diagram for encryption according to the proposed method; Figure 4 shows more detailed signaling during a certain time interval according to Figure 3; EMBODIMENT INFORMATIONS Figure 1 schematically shows two base stations B51 and B82 and a mobile MS which is assumed to move from the base station BS1 towards the base station BS2. The base station BS1 serves traffic within the cell C1 and the base station B52 serves traffic within the cell CZ.
Cellerna Cl och C2 har en gemensam gräns G. Då mobilen M närmar sig denna gräns sjunker talkvalitén för ett uppkopplat samtal som betjänas av bassta- tionen BSl över en viss radiokanal Kl. Genom mätning av radiosignalens fältstyrka och beräkning enligt kända principer utförs en överföring av en ny radiokanal KZ till MS från B51. Denna nya kanal KZ betjänas av B52. Under själva omkopplingsförloppet som varar ca 100 ms sker ingen mottagning av MS och mottagningskretsarna i MS kan förlora trafikflödets synkronism dvs tids- läget hos ramar och tidsluckor från basstation BSl.The cells C1 and C2 have a common limit G. As the mobile M approaches this limit, the speech quality of a connected call served by the base station BS1 drops over a certain radio channel K1. By measuring the field strength of the radio signal and calculating according to known principles, a transmission of a new radio channel KZ to MS is performed from B51. This new channel KZ is served by B52. During the actual switching process, which lasts about 100 ms, no reception of MS takes place and the reception circuits in MS can lose the synchronism of the traffic flow, ie the time position of frames and time slots from base station BS1.
Figur 2 visar en sändande ram och en mottagande ram (RX respektive TX) för mobilen MS.Figure 2 shows a transmitting frame and a receiving frame (RX and TX, respectively) for the mobile MS.
Det antas att trafikflödet före "hand-off" är krypterat med en viss nyckel E2.It is assumed that the traffic flow before "hand-off" is encrypted with a certain key E2.
Denna nyckel utgörs av en bitsekvens eller ett avsnitt av en längre slumpmässig bitsekvens E (exempelvis ca 3 minuter läng), som överlagras trafikflödet genom modulo 2-addition bit för bit. Nyckeln E är givetvis känd för mobilen iviS om denna är behörig att sända och motta samtal, och vidare sänder basstation BSl uppgift om starttidpunkten dvs var i sekvensen E bitflödet skall påbörjas, dvs E2 är känd för mobilen MS. Denna krypteringsteknik är förut känd.This key consists of a bit sequence or a section of a longer random bit sequence E (for example about 3 minutes long), which is superimposed on the traffic flow by modulo 2-addition bit by bit. The key E is of course known for the mobile iviS if it is authorized to send and receive calls, and furthermore base station BS1 sends information about the start time, ie where in the sequence E the bit flow is to start, ie E2 is known for the mobile MS. This encryption technique is known in the art.
Figur 3 visar i ett tidsdiagram hur metoden tillämpas vid "hand-off". Det antas att basstationen BSl kommunicerar med mobilen MS och att kommunikationen (talet) är krypterat medelst en kryptonyckel E2 fram till tiden tl. Vid tiden tl sker hand-off.Figure 3 shows in a time diagram how the method is applied at "hand-off". It is assumed that the base station BS1 communicates with the mobile MS and that the communication (number) is encrypted by means of a cryptographic key E2 until the time t1. At the time tl takes place hand-off.
Vid "hand-off" förloppets slut vid tiden tz har MS synkroniserat in sig till den nya basstationen BS2. Fran denna basstation utsändes nämligen på en viss 464 553 10 15 20 25 30 4 styrkanal (SY enligt figur 2) en synkroniseringssekvens under tiden tl-tz som anger tidsläget för ramarna och den tilldelade tidsluckan för den fortsatta samtalskommunikationen mellan B52 och MS. Detta görs på i och för sig känt sätt medelst ett korrelationsförfarande i MS. Vid tiden t=t2 finns således ramsynkronisering för tal/data överföring mellan BS2 och MS men ej för krypteringen. Basstationen BS2 utsänder vid t=t2 en okrypterad signal som anger när krypteringen enligt nyckeln E2 åter påbörjas, dvs BS2 meddelar tidpunkten 1:3. Enligt den föreslagna metoden krypteras trafikflödet (tal/data) i efterföljande ramar med en nyckel El som utgörs av en periodisk slumpmässig bitsekvens med en period = ramintervallet. Härigenom kan mobilen MS räkna det antal ramintervall som skall förflyta (meddelat genom den okrypterade signalen) till dess att kryptering enligt nyckeln EZ påbörjas av B52.At the end of the "hand-off" process at time tz, the MS has synchronized with the new base station BS2. Namely, from this base station, on a certain control channel (SY according to Figure 2), a synchronization sequence was transmitted during the time t1-tz which indicates the time position of the frames and the assigned time slot for the continued call communication between B52 and MS. This is done in a manner known per se by means of a correlation method in MS. At time t = t2 there is thus frame synchronization for speech / data transmission between BS2 and MS but not for the encryption. The base station BS2 transmits at t = t2 an unencrypted signal which indicates when the encryption according to the key E2 is started again, ie BS2 announces the time 1: 3. According to the proposed method, the traffic flow (speech / data) in subsequent frames is encrypted with a key E1 which consists of a periodic random bit sequence with a period = frame interval. In this way, the mobile MS can count the number of frame intervals to pass (communicated by the unencrypted signal) until encryption according to the key EZ is started by B52.
Figur 4 visar närmare förloppet under tidsintervallet t -t . 2 3 Vid tiden t2 är enligt figur 3 mobilen M5 synkroniserad till den nya basstationen BS2 och det normala trafikflödet (data, tal, synkronisering) skulle ha påbörjats om ej nagon kryptering hade använts. Synkroniseringen för bitflödet i kryp- teringsnyckein E2 fram till tiden tl, har emellertid gått förlorad. Basstationen sänder därför ut en signal S1 till MS som anger hur många ramar som skall förflyta till dess att kryptering enligt nyckel E2 kommer att påbörjas. I figur 4 antas detta ramantal vara 13. Detta meddelande kan utsändas okrypterat på den s k FACCH (fast associated control channel), vilket bildas av en reserverad tidslucka inom en ram, se figur 2. Denna tidslucka befinner sig således i ram Rl. Under de därpå följande ramarna R2, RB, R6 överförs samtalsinforma- tion som är krypterad med nyckel El. Denna nyckel är som ovan nämnts en periodisk bitsekvens, vars period = ett ramintervall och som överlagras samtals- informationen genom modulo-2 addition. Mobilen MS vet därför dels starttid- punkten för räkningen dels hur många ramintervall som skall uppräknas. Om mobilen uppfattat detta skickas en bekräftelsesignal Al tillbaks till bassta- tionen B52, vilken mottas i ram R6. Om basstationen BS2 mottar denna signal väntar den en tid = det överenskomna antalet ramar dvs till ram Rl3 (t=t3) då kryptering enligt nyckeln EZ påbörjas.Figure 4 shows in more detail the process during the time interval t -t. At time t2, according to Figure 3, the mobile M5 is synchronized to the new base station BS2 and the normal traffic flow (data, speech, synchronization) would have started if no encryption had been used. However, the synchronization of the bit flow in the encryption key E2 up to the time t1 has been lost. The base station therefore sends a signal S1 to the MS which indicates how many frames are to flow until encryption according to key E2 will be started. In Figure 4, this number of frames is assumed to be 13. This message can be transmitted unencrypted on the so-called FACCH (fast associated control channel), which is formed by a reserved time slot within a frame, see Figure 2. This time slot is thus in frame R1. During the subsequent frames R2, RB, R6, call information which is encrypted with key E1 is transmitted. This key is, as mentioned above, a periodic bit sequence, whose period = a frame interval and which is superimposed on the call information by modulo-2 addition. The mobile MS therefore knows both the start time of the calculation and how many frame intervals are to be calculated. If the mobile has perceived this, a confirmation signal A1 is sent back to the base station B52, which is received in frame R6. If the base station BS2 receives this signal, it waits a time = the agreed number of frames, ie to frame R13 (t = t3) when encryption according to the key EZ is started.
Basstationen B52 väntar således en viss tid (i figur 4 en tid = 5 ramintervall) på bekräftelsesignalen Al. Om denna signal av någon anledning ej mottas av ru 10 4s4isšs 5 basstationen BS2 inom en viss tid utsänds en signal S2 i ram R7 pà nytt och en ny bekräftelsesignal A2 avvaktas. Signalen Al kan bortfalla pà grund av exempelvis fading eller svåra omgivningsförhållanden i just det intervall signa- len Al utsändes. Det från basstationen B52 meddelade antalet ramar (=Rl3) bör således väljas sa stort att upprepad signalering enligt ovan kan utföras.Thus, the base station B52 waits a certain time (in Fig. 4 a time = 5 frame intervals) for the acknowledgment signal A1. If for some reason this signal is not received by the base station BS2 within a certain time, a signal S2 in frame R7 is retransmitted and a new acknowledgment signal A2 is awaited. The signal A1 can be lost due to, for example, fading or difficult ambient conditions in the exact interval at which the signal A1 was transmitted. The number of frames (= R13) communicated from the base station B52 should thus be chosen so large that repeated signaling as above can be performed.
Signalfördröjningen mellan basstation och mobil har enligt figur 4 antagits vara ca 2-3 ramintervall (z 15 ms). Denna fördröjning bör även beaktas. Företrädes- vis bör alltså krypteringstidpunkten t3 väljas så att 1:2 - t; > 4 gànger max. utbredningstiden. Beräkning av denna erbjuder inga svårigheter, eftersom mobilen befiner sig på gränsen mellan tvâ celler Cl, C2 enligt figur 1, dvs pä ett maximalt avstånd från en basstation.According to Figure 4, the signal delay between base station and mobile has been assumed to be approximately 2-3 frame intervals (z 15 ms). This delay should also be taken into account. Preferably, therefore, the encryption time t3 should be chosen so that 1: 2 - t; > 4 times max. the propagation time. Calculation of this offers no difficulties, since the mobile is located at the boundary between two cells C1, C2 according to Figure 1, i.e. at a maximum distance from a base station.
Claims (3)
Priority Applications (14)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8902994A SE464553B (en) | 1989-09-12 | 1989-09-12 | METHOD OF SYNCHRONIZATION IN A MOBILE RADIO SYSTEM |
JP2512660A JP2978243B2 (en) | 1989-09-12 | 1990-07-19 | Synchronization method for mobile radio systems |
AU63535/90A AU625469B2 (en) | 1989-09-12 | 1990-07-19 | Synchronizing method in a mobile radio system |
PCT/SE1990/000497 WO1991004620A1 (en) | 1989-09-12 | 1990-07-19 | Synchronizing method in a mobile radio system |
KR1019910700472A KR970002747B1 (en) | 1989-09-12 | 1990-07-19 | Synchronizing method in a mobile radio system |
CA002039699A CA2039699C (en) | 1989-09-12 | 1990-07-19 | Synchronizing method in a mobile radio system |
NZ234720A NZ234720A (en) | 1989-09-12 | 1990-07-31 | Mobile radio: passing location of next synchronising frame |
GB9017473A GB2236458B (en) | 1989-09-12 | 1990-08-09 | Synchronizing method in a mobile radio system |
MYPI90001333A MY106831A (en) | 1989-09-12 | 1990-08-09 | Synchronizing method in a mobile radio system. |
DE4026698A DE4026698C2 (en) | 1989-09-12 | 1990-08-23 | Synchronization procedure in a mobile radio system |
FR909011029A FR2652468B1 (en) | 1989-09-12 | 1990-09-05 | SYNCHRONIZATION METHOD IN A MOBILE RADIO SYSTEM. |
CN90107657A CN1023283C (en) | 1989-09-12 | 1990-09-12 | Synchronizing method in mobile radio system |
US07/987,244 US5293423A (en) | 1989-09-12 | 1992-12-07 | Synchronizing method in a mobile radio system |
HK58695A HK58695A (en) | 1989-09-12 | 1995-04-20 | Synchronizing method in a mobile radio system. |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8902994A SE464553B (en) | 1989-09-12 | 1989-09-12 | METHOD OF SYNCHRONIZATION IN A MOBILE RADIO SYSTEM |
Publications (3)
Publication Number | Publication Date |
---|---|
SE8902994D0 SE8902994D0 (en) | 1989-09-12 |
SE8902994L SE8902994L (en) | 1991-03-13 |
SE464553B true SE464553B (en) | 1991-05-06 |
Family
ID=20376856
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
SE8902994A SE464553B (en) | 1989-09-12 | 1989-09-12 | METHOD OF SYNCHRONIZATION IN A MOBILE RADIO SYSTEM |
Country Status (13)
Country | Link |
---|---|
JP (1) | JP2978243B2 (en) |
KR (1) | KR970002747B1 (en) |
CN (1) | CN1023283C (en) |
AU (1) | AU625469B2 (en) |
CA (1) | CA2039699C (en) |
DE (1) | DE4026698C2 (en) |
FR (1) | FR2652468B1 (en) |
GB (1) | GB2236458B (en) |
HK (1) | HK58695A (en) |
MY (1) | MY106831A (en) |
NZ (1) | NZ234720A (en) |
SE (1) | SE464553B (en) |
WO (1) | WO1991004620A1 (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2260245B (en) * | 1991-10-04 | 1995-03-08 | Technophone Ltd | Digital radio receiver |
WO1994022245A1 (en) * | 1993-03-23 | 1994-09-29 | Telefonaktiebolaget Lm Ericsson | A method for cascading of microbases |
CN1510936B (en) * | 1997-04-24 | 2010-05-26 | 株式会社Ntt都科摩 | Mobile communication method of mobile communication system |
FR2809579B1 (en) * | 2000-05-23 | 2003-07-04 | Nortel Matra Cellular | METHOD FOR CONTROLLING A CHANNEL BETWEEN A RADIO TERMINAL AND A CELLULAR RADIO COMMUNICATION INFRASTRUCTURE, AND ACCESS NETWORK IMPLEMENTING SUCH A METHOD |
FR2809576B1 (en) * | 2000-05-23 | 2002-11-15 | Nortel Matra Cellular | METHOD FOR CONTROLLING A CHANNEL BETWEEN A RADIO TERMINAL AND A CELLULAR RADIO COMMUNICATION INFRASTRUCTURE, AND ACCESS NETWORK IMPLEMENTING SUCH A METHOD |
DE10056361A1 (en) * | 2000-11-14 | 2002-05-23 | Philips Corp Intellectual Pty | Wireless network for the transmission of parameters for encrypted data transmission |
CN102572820B (en) * | 2004-11-02 | 2015-11-11 | 苹果公司 | The method used together with OFDM and base station thereof and wireless terminal |
KR100902112B1 (en) * | 2006-11-13 | 2009-06-09 | 한국전자통신연구원 | Insertion method and transmission method of vector information for voice data estimating in key re-synchronization, and voice data estimating method in key re-synchronization using vector information |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1429469A (en) * | 1961-07-19 | 1976-03-24 | Hell Rudolf | Method for subsequently setting data receivers in a contrinuous transmission of encoded data transmitted in binary code form |
DE978043C (en) * | 1962-08-27 | 1977-04-21 | Siemens Ag | Method and device for the encrypted transmission of telex messages |
EP0028272A1 (en) * | 1979-11-03 | 1981-05-13 | PATELHOLD Patentverwertungs- & Elektro-Holding AG | Method and device for the transmission of enciphered information |
US4411017A (en) * | 1980-03-14 | 1983-10-18 | Harris Corporation | Secure mobile telephone system |
US4555805A (en) * | 1980-03-14 | 1985-11-26 | Harris Corporation | Secure mobile telephone system |
DE3150254A1 (en) * | 1981-04-13 | 1983-07-14 | Siemens AG, 1000 Berlin und 8000 München | DEVICE FOR ENCRYPTED DIGITAL INFORMATION TRANSFER |
US4549308A (en) * | 1982-07-12 | 1985-10-22 | At&T Bell Laboratories | Secure mobile radio telephony |
TR23067A (en) * | 1985-07-12 | 1989-02-21 | Siemens Ag | A METHOD AND EQUIPMENT TO INCRETE THE ENCRYPED RADIO TRAFFIC |
JPS62137937A (en) * | 1985-12-12 | 1987-06-20 | Fujitsu Ltd | Line changeover system |
US4803726A (en) * | 1986-12-31 | 1989-02-07 | Motorola, Inc. | Bit synchronization method for a digital radio telephone system |
-
1989
- 1989-09-12 SE SE8902994A patent/SE464553B/en not_active IP Right Cessation
-
1990
- 1990-07-19 JP JP2512660A patent/JP2978243B2/en not_active Expired - Lifetime
- 1990-07-19 KR KR1019910700472A patent/KR970002747B1/en not_active IP Right Cessation
- 1990-07-19 WO PCT/SE1990/000497 patent/WO1991004620A1/en active Application Filing
- 1990-07-19 CA CA002039699A patent/CA2039699C/en not_active Expired - Fee Related
- 1990-07-19 AU AU63535/90A patent/AU625469B2/en not_active Ceased
- 1990-07-31 NZ NZ234720A patent/NZ234720A/en unknown
- 1990-08-09 GB GB9017473A patent/GB2236458B/en not_active Expired - Fee Related
- 1990-08-09 MY MYPI90001333A patent/MY106831A/en unknown
- 1990-08-23 DE DE4026698A patent/DE4026698C2/en not_active Expired - Fee Related
- 1990-09-05 FR FR909011029A patent/FR2652468B1/en not_active Expired - Lifetime
- 1990-09-12 CN CN90107657A patent/CN1023283C/en not_active Expired - Fee Related
-
1995
- 1995-04-20 HK HK58695A patent/HK58695A/en not_active IP Right Cessation
Also Published As
Publication number | Publication date |
---|---|
MY106831A (en) | 1995-07-31 |
DE4026698C2 (en) | 1999-06-17 |
AU625469B2 (en) | 1992-07-09 |
AU6353590A (en) | 1991-04-18 |
DE4026698A1 (en) | 1991-03-14 |
FR2652468A1 (en) | 1991-03-29 |
CN1050294A (en) | 1991-03-27 |
GB2236458A (en) | 1991-04-03 |
CN1023283C (en) | 1993-12-22 |
KR920702120A (en) | 1992-08-12 |
FR2652468B1 (en) | 1992-07-03 |
JPH04501944A (en) | 1992-04-02 |
WO1991004620A1 (en) | 1991-04-04 |
GB2236458B (en) | 1993-10-13 |
CA2039699A1 (en) | 1991-03-13 |
KR970002747B1 (en) | 1997-03-10 |
HK58695A (en) | 1995-04-28 |
CA2039699C (en) | 1999-09-28 |
GB9017473D0 (en) | 1990-09-26 |
SE8902994L (en) | 1991-03-13 |
SE8902994D0 (en) | 1989-09-12 |
JP2978243B2 (en) | 1999-11-15 |
NZ234720A (en) | 1992-12-23 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
AU649908B2 (en) | A method of transmitting synchronizing information in the ciphered transmission of data in a mobile radio system | |
US5293423A (en) | Synchronizing method in a mobile radio system | |
US3829777A (en) | Control system for diversity transmission in a terrestrial station of satellite communication | |
KR0140130B1 (en) | Digital communication system | |
FI106494B (en) | Ramsynkroniseringsmekanism | |
JP4481447B2 (en) | Synchronization method | |
US6021333A (en) | Method and system for transferring information within a mobile communication system | |
KR960011190B1 (en) | Continuous cipher synchronization for cellular communication system | |
US3823269A (en) | Speech path test system for time-division switching equipment | |
SE500826C2 (en) | Method of disconnecting an established communication connection in a mobile radio system | |
SE464553B (en) | METHOD OF SYNCHRONIZATION IN A MOBILE RADIO SYSTEM | |
JPS6069924A (en) | Ringing signal transmitting system | |
US4631721A (en) | Bidirectional communication system of a two-wire bus comprising an active terminator | |
JPH11146444A (en) | Synchronization establishing system for mobile communication base station network | |
US3597547A (en) | Apparatus for synchronizing a pcm-receiver and a transmitter | |
EP0479950A4 (en) | Synchronization and equalization in a tdma cellular system | |
CN101167380A (en) | Method and apparatus for generating session keys | |
EP0938787B1 (en) | Method for reducing interference within signaling data over an air interface | |
JPH082117B2 (en) | Channel switching method | |
US2412955A (en) | Telegraph switching system | |
JPS6093868A (en) | Data telephone terminal test equipment | |
JP2757775B2 (en) | System clock matching system and telephone switching network with system clock matching function | |
JPH0819038A (en) | Inter-station synchronization system between radio base stations | |
US2272412A (en) | Multiplex drop channel repeater | |
JPH08154271A (en) | Inter-base-station synchronization device in digital cordless telephone system |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
NAL | Patent in force |
Ref document number: 8902994-6 Format of ref document f/p: F |
|
NUG | Patent has lapsed |
Ref document number: 8902994-6 Format of ref document f/p: F |