tokens: ['The', 'logical', 'control', 'channels', 'are', 'defined', 'in', 'GPP', 'TS', '', '', 'In', 'the', 'following', 'those', 'control', 'channels', 'are', 'considered', 'which', 'carry', 'signalling', 'information', 'or', 'specific', 'types', 'of', 'user', 'packet', 'information', 'i', 'Broadcast', 'Control', 'CHannel', 'BCCH', 'downlink', 'only', 'used', 'to', 'broadcast', 'Cell', 'specific', 'information', 'ii', 'Synchronization', 'CHannel', 'SCH', 'downlink', 'only', 'used', 'to', 'broadcast', 'synchronization', 'and', 'BSS', 'identification', 'information', 'iii', 'Paging', 'CHannel', 'PCH', 'downlink', 'only', 'used', 'to', 'send', 'page', 'requests', 'to', 'Mobile', 'Stations', 'MSs', 'iv', 'Random', 'Access', 'CHannel', 'RACH', 'uplink', 'only', 'used', 'to', 'request', 'a', 'Dedicated', 'Control', 'CHannel', 'v', 'Access', 'Grant', 'CHannel', 'AGCH', 'downlink', 'only', 'used', 'to', 'allocate', 'a', 'Dedicated', 'Control', 'CHannel', 'vi', 'Standalone', 'Dedicated', 'Control', 'CHannel', 'SDCCH', 'bidirectional', 'vii', 'Fast', 'Associated', 'Control', 'CHannel', 'FACCH', 'bidirectional', 'associated', 'with', 'a', 'Traffic', 'CHannel', 'viii', 'Slow', 'Associated', 'Control', 'CHannel', 'SACCH', 'bidirectional', 'associated', 'with', 'a', 'SDCCH', 'or', 'a', 'Traffic', 'CHannel', 'ix', 'Cell', 'Broadcast', 'CHannel', 'CBCH', 'downlink', 'only', 'used', 'for', 'general', 'not', 'point', 'to', 'point', 'short', 'message', 'information', 'x', 'Notification', 'CHannel', 'NCH', 'downlink', 'only', 'used', 'to', 'notify', 'mobile', 'stations', 'of', 'VBS', 'Voice', 'Broadcast', 'Service', 'calls', 'or', 'VGCS', 'Voice', 'Group', 'Call', 'Service', 'calls', 'Two', 'service', 'access', 'points', 'are', 'defined', 'on', 'signalling', 'layer', '', 'which', 'are', 'discriminated', 'by', 'their', 'Service', 'Access', 'Point', 'Identifiers', 'SAPI', 'see', 'GPP', 'TS', '', '', 'i', 'SAPI', '', 'supports', 'the', 'transfer', 'of', 'signalling', 'information', 'including', 'useruser', 'information', 'ii', 'SAPI', '', 'supports', 'the', 'transfer', 'of', 'user', 'short', 'messages', 'Layer', '', 'selects', 'the', 'service', 'access', 'point', 'the', 'logical', 'control', 'channel', 'and', 'the', 'mode', 'of', 'operation', 'of', 'layer', '', 'acknowledged', 'unacknowledged', 'or', 'random', 'access', 'see', 'GPP', 'TS', '', '', 'and', 'GPP', 'TS', '', '', 'as', 'required', 'for', 'each', 'individual', 'message']