[54] METHODS AND APPARATUS FOR EXCLUDING COMMUNICATION CHANNELS IN A RADIO TELEPHONE
[75] Inventors: Nguyen Quan Tat; Robert Stanley Saunders, both of Surrey, England
[73] Assignee: Nokia Mobile Phones Limited, Salo, Finland
[21] Appl. No.: 584,109
[22] Filed: Jan. 11, 1996
[30] Foreign Application Priority Data
Jan. 10, 1995 [GB] United Kingdom 9500799
[51] Int. CI. H04B 7/212
[52] U.S. CI 370/330; 370/337; 370/332
[58] Field of Search 370/280, 337,
370/330, 331, 332, 329, 321, 341, 347, 442, 458; 455/33.1, 33.2, 34.1, 56.1, 54.1, 54.2, 67.1, 509, 514, 515, 422, 450, 452,
436-438
[56] References Cited
U.S. PATENT DOCUMENTS
5.134.709 7/1992 Bi et al 455/33.1
5.134.710 7/1992 Akerberg 455/54.1
5,150,362 9/1992 Akerberg 370/331
5,175,758 12/1992 Levanto et al 379/57
5,200,956 4/1993 Pudney et al 370/337
5,210,752 5/1993 Ito et al. .
5,210,771 5/1993 Schaeffer et al. .
5,258,981 11/1993 Davey et al 370/337
5,345,448 9/1994 Keskitalo .
5,394,391 2/1995 Chen et al. .
5,396,496 3/1995 Ito et al 370/330
5,410,733 4/1995 Niva et al 455/33.2
5,416,778 5/1995 Chan et al 370/337
5,483,668 1/1996 Malkamaki et al 455/33.2
5,598,407 1/1997 Bud et al 370/330
FOREIGN PATENT DOCUMENTS
2249918 5/1992 United Kingdom .
Primary Examiner—Chau Nguyen
Attorney, Agent, or Firm—Perman & Green, LLP
[57] ABSTRACT
A portable radio telephone (5) communicates with base stations (1, 2) in a digital radio telephone system, such as DECT, employing TDMA transmission. The portable radio telephone is programmed with an algorithm which is operative to select a communication channel by storing a blind slot mask (7) representative of the time slots in each frame which are excluded, either by virtue of being occupied by the base station or by the portable radio telephone itself. Hence, any channel attempted and failed in an occupied time slot is excluded and marked blind in the blind slot mask. Further, the algorithm is operative to check the time slots for availability in a predetermined sequence which corresponds to the temporal sequence of the slots (or the reverse thereof) to promote orderly filling of the time slots at the base stations.
15 Claims, 6 Drawing Sheets
