2 Outline Introduction Masters, Slaves, and Piconets System Timing Physical Links: SCO and ACL Bluetooth Packets Logical Channels Synchronization
3 Scope Higher Protocol Stack Link Manager (LM) Link Controller (LC) Baseband RF
4 Link Controller & Baseband (1) LM LC Link-level and medium access management Packet-level access control PHY: Baseband: packet-level processing and timing RF
5 Link Controller & Baseband (2) LC: commanded by LM Local & remote LC entities manage the packet-by-packet process of establishing the link Maintain the link once established Baseband: commanded by LC Channel coding/decoding Low-level timing control and management
6 Link Controller & Baseband in the Bluetooth Spec.
7 Bluetooth Device Address BD_Addr[47:32] (NAP[15:0]) Used to initialize the encryption engine stream LFSR BD_Addr[31:24] (UAP[7:0]) Used to initialize the HEC and CRC calculation for frequency hopping BD_Addr[23:0] (LAP[23:0]) Used by sync word generation and frequency hopping
8 Masters, Slaves, and Piconets Master the device which initiates an exchange of data Slave the device which responds to the master
9 Time Division Multiplexing and Time Slots 625 µs/slot CLKN (312.5 µs): 0 to , cyclic
10 Multi-Slot Packets
11 Frequency Hopping Hopping Mechanism All devices in a piconet hops in synchrony with the Master Each device will hop once per packet* Benefits Security Reliability Tradeoff *equivalent for multi-slot packets
12 Hopping Sequence A pseudo-randomly determined frequency sequence Clocks CLKN native clock of the device CLK Master clock of the piconet CLKN of the piconet Master device CLKE estimate of CLKN of the slaves Hopping sequence determined by the Master (CLK and Master LAP)
13 Piconet and Scatternet (1) Two or more units sharing the same hopping sequence form a piconet (similar to a LAN) Each piconet can have only one master up to seven slaves Multiple piconets form a scatternet
18 Simple Calculations ±10us, ±20ppm between the Master and Slaves Allows for a Salve to be left alone for up to 800 slots DH5: 2870µs x 40ppm = 0.12 µs (1/8 symbol period) very simple timing recovery (20 µs / 625 µs ) / 40ppm = 800
20 ACL An ACL link is formed immediately after a connection is established. A Master may have multiple ACL links to the slaves, but only one link can exist between any two devices. A slave is permitted to return an ACL packet in the slave-to-master( ) slot if and only if it has been addressed in the preceding master-toslave slot( ). Broadcast packets are ACL packets not addressed to any specific slaves.
21 SCO A SCO provides a symmetric link between Master and Slave with reserved channel bandwidth and slots. A Master can support up to three SCO links. A slave can support up to three SCO links from the same master two SCO links if the links are originated from different masters. SCO packets are never retransmitted. SCO > ACL
22 SCO T SCO, D SCO, and SCO interval SCO is setup via the Link Manager Protocol (LMP). LMP control messages (e.g. broadcast) > SCO slots Initialization Master CLK[27:1] mod T SCO = D SCO Master (CLK, CLK[26:1]) mod T SCO = D SCO
23 Bluetooth Packets Little Endian Each packet consists of 3 entities: Access code Header Payload
24 Access Code To catch A broadcast packet The packet to a specific slave Actions involved DC offset compensation Clock recovery and Synchronization Identification
25 Different Access Codes (1) Channel Access Code (CAC) Derived from Master s LAP and CLKN Used by all devices in a piconet during connection Device Access Code (DAC) Derived from a specific device s LAP and CLKN Used in Paging/Page Scan
26 Different Access Codes (2) Inquiry Access Code (IAC) General Inquiry Access Code (GIAC) Used by all devices during the inquiry procedures, as no prior knowledge of anyone s LAP exists. Fixed (0x9E8B33) Dedicated Inquiry Access Code (DIAC) For the inquiry of specific set of devices like printers and handsets 0x9E8B00 0x9E8B3F Generic Access Profile indicates only the Limited Inquiry Access Code (LIAC, 0x9E8B00) should be used. Use on a temporary basis
27 Different Access Codes (3)
28 Access Code Format
29 Access Code Preamble The sequence 1010 or 0101, depending on whether the LSB of the following sync word is 1 or 0. This gives the DC thresholding and clock recovery circuitry only 5µs to create a reliable clock signal, with which to sample and clock in the remainder of the data.
30 Access Code Trailer The trailer sequence is either 1010 or 0101 depending on whether the MSB of the sync word is 0 or 1.
31 Access Code Sync Word Total 64 bits. The 34-bit BCH parity word is the key element of the sync word very high autocorrelation very low co-correlation BCH Parity Word LAP Barker Sequence 34 bits 24 bits 6 bits
32 Access Code Sync Word Sync word Match: the packet is intended for the receiving device. No-match: the radio can be shut down to conserve power. The point in time at which the correlator match Master is exactly 68ms into its slots. This allows the Slave to re-adjust its own subslot timing to match up with the Master to within 1 ms.
34 Header Protection against Erross Each field is crucial total 18 bits protected by a Forward Error Correction (FEC) code of 1/3, resulting in 54 bits.
35 Header AM_ADDR Distinguishes the active members participating on the piconet. Max. of 7 slaves 3 bits The all-zero address is reserved for broadcasting packets, with the FHS packet as the only exception.
36 Header TYPE Types of traffic: SCO, ACL, NULL, POLL, ID, FHS. Types of error correction used for the payload. How many slots the payload will last.
38 Header FLOW Used for flow control of packets over the ACL link. When the RX buffer in the recipient is full and is not emptied, FLOW=0 is returned to stop the transmission of data temporarily. Only applicable to ACL packets. Packets containing only link control information (ID, POLL, and NULL packets) or SCO packets can still be received. When the RX buffer is empty, FLOW=1 is returned. When no packet is received, or the received header is in error, FLOW=1 is assumed implicitly.
39 Header ARQN ARQN=1(0) informs the sender of a successful (failed) transfer of payload data with a cyclic redundancy check (CRC) code Positive acknowledge: ACK Negative acknowledge: NAK When no return message regarding acknowledge is received, a NAK is assumed and data is re-transmitted. NAK is also the default return information.
40 Packet Header SEQN The SEQN bit provides a sequential numbering scheme to order the data packet stream. For each new transmitted packet that contains data with CRC, the SEQN bit is inverted. By comparing the SEQN of consecutive packets, correctly received retransmissions can be discarded.
41 Header HEC Header Error Check (HEC) is simply a CRC function performed on the header. The HEC consists of an 8-bit word generated by the polynomial 647(octal representation). Before generating the HEC, the HEC generator is initialized with an the Master or Slave UAP or All-zero 8-bit values, depending on the packet. If the HEC does not pass, the entire packet is discarded.
43 Payload Content ACL packets only have the data field. SCO packets only have the voice field with the exception of the DV packets. Voice Field 240 bits for HV packets 80 bits for DV packets
44 Payload Data Field (1) Payload Header [8 or 16] Payload [0-2712] CRC  L_CH  Flow  Length [5 or 9] Undefined [0 or 4]
45 Payload Data Field (2) Packets in segments 1 & 2 have a 1-byte payload header (see Packet Types) Packets in segments 3 & 4 have a 2-bytes payload header (see Packet Types) The payload header specifies the logical channel (L_CH), controls the flow on the logical channels (FLOW), and the payload length (5 bits and 9 bits for 1-byte and 2-bytes payload header, respectively). In the case of a 2-byte payload header, the length indicator is extended by four bits into the next byte. The remaining four bits of the second byte are reserved for future use and shall be set to zero.
46 Payload Header (Data Field) L_CH 00 Undefined 01 Continue of an L2CAP message 10 Start of an L2CAP message 11 LMP message FLOW Flow control at the L2CAP level (1 if L_CH=11) Set by LM No real-time requirements (real-time flow control at packet level is carried out via the FLOW bit in the packet header)
47 CRC The 16-bit CRC code is generated by the CRC- CCITT polynomial (octal representation). Before determining the CRC code, an 8-bit value is used to initialize the CRC generator. For the CRC code in the FHS packets sent in master page response state, the UAP of the slave is used. For the FHS packet sent in inquiry response state, the DCI (all-zero) is used. For all other packets, the UAP of the master is used.
48 Packet Types (1) It is the responsibility of LM to monitor the quality and reliability of the link and decide what packet types to use at any given time. LMP_max_slot_req LMP_accepted, LMP_not_accepted Single-slot packet is used by default. Asymmetric bandwidth different packet type in different transmission directions
50 Packet Types (2) Segment 1 (NULL, POLL, FHS, DM1): reserved for the four control packets common to all physical link types. Segment 2 (HV1-3, DV, DH, AUX1): reserved for packets occupying a single time slot. Segment 3 (DM3, DH3): reserved for packets occupying three time slots. ACL defined only. Segment 4 (DM5, DH5): reserved for packets occupying five time slots. ACL defined only.
51 Common Packet Types ID packet NULL packet POLL packet FHS packet DM1 packet
52 ID Packet The identity (ID) packet consists of the device access code (DAC) or inquiry access code (IAC). It has a fixed length of 68 bits. It is a very robust packet since the only info it carries is the access code of the sender.
53 NULL Packet The NULL packet has no payload and therefore consists of the channel access code and packet header only. Its total (fixed) length is 126 bits. The NULL packet is used to return link information to the source regarding the success of the previous transmission (ARQN), or the status of the RX buffer (FLOW).
54 POLL Packet Similar to the NULL packet does not have a payload In contrast to the NULL packet requires a confirmation from the recipient Used by the master in a piconet to check the presence of the slaves, which must then respond even if they do not have information to send. The return packet is an implicit acknowledgement of the POLL packet. The POLL packet does not affect the ARQN and SEQN fields.
55 FHS Packet (1) A special control packet revealing, among other things, the Bluetooth device address and the clock of the sender. The payload contains 144 information bits plus a 16- bit CRC code. The payload is coded with a rate 2/3 FEC which brings the gross payload length to 240 bits. Used in page master response, inquiry response and in master slave switch. The payload consists of 11 fields.
56 FHS Packet (2) BCH Parity Word
57 FHS Packet (3)
59 FHS Packet (5)
60 FHS Packet (6)
61 DM1 Packet Data Medium rate DM1 serves as part of segment 1 in order to support control messages in any link type. However, it can also carry regular user data. Since the DM1 packet is recognized on the SCO link, it can interrupt the synchronous information to send control information.
62 SCO Packets Typically used for 64kb/s speech transmission HV1 packet HV2 packet HV3 packet DV packet
63 HV1 Packet High-quality Voice The HV1 packet carries 10 information bytes. The bytes are protected with a rate 1/3 FEC. Payload length is fixed at 240 bits. No CRC. No payload header. A HV1 packet can carry 1.25ms of speech at a 64 kb/s rate. In that case, an HV1 packet has to be sent every two time slots (T SCO =2).
64 HV2 Packet The HV2 packet carries 20 information bytes protected with a rate 2/3 FEC. The payload length is fixed at 240 bits. No payload header, No CRC. If the HV2 packet is used for voice at a 64 kb/s rate, it can carry 2.5ms of speech. In that case, an HV2 packet has to be sent every four time slots (T SCO =4).
65 HV3 Packet The HV3 packet carries 30 information bytes. The bytes are not protected by FEC. The payload length is fixed at 240 bits. No CRC. No payload header. If the HV3 packet is used for voice at a 64 kb/s rate, it can carry 3.75ms of speech. In that case, an HV3 packet has to be sent every six time slots (T SCO =6).
66 DV Packet (1) The DV packet is a combined data-voice packet. The payload is divided into a voice field of 80 bits and a data field containing up to 150 bits. The voice field is not protected by FEC. The data field contains up to 10 infor-mation bytes (including the 1-byte payload header) and includes a 16-bit CRC. The data field is encoded with a rate 2/3 FEC. The voice field is handled like normal SCO data and is never retransmitted; that is, the voice field is always new. The data field is checked for errors and is retransmitted if necessary.
69 DM1 Packet The DM1 packet is a packet that carries data information only. The payload contains up to 18 information bytes (including the 1-byte payload header) plus a 16-bit CRC code. The DM1 packet may cover up to a single time slot. The information plus CRC bits are coded with a rate 2/3 FEC which adds 5 parity bits to every 10-bit segment. If necessary,extra zeros are appended after the CRC bits to get the total number of bits(information bits, CRC bits, and tail bits) equal a multiple of 10. The payload header in the DM1 packet is only 1 byte long. The length indicator in the payload header specifies the number of user bytes(excluding payload header and the CRC code).
70 DH1 Packet This packet is similar to the DM1 packet, except that the information in the pay-load is not FEC encoded. DH1 packet can carry up to 28 information bytes plus a 16-bit CRC code. The DH1 packet may cover up to a single time slot.
71 DM3 Packet The DM3 packet is a DM1 packet with an extended payload. The DM3 packet may cover up to three time slots. The payload contains up to 123 information bytes (including the 2-bytes payload header) plus a 16-bit CRC code. The payload header in the DM3 packet is 2 bytes long, The length indicator in the payload header specifies the number of user bytes (excluding payload header and the CRC code). When a DM3 packet is sent or received, the RF hop frequency shall not change for a duration of three time slots (the first time slot being the slot where the channel access code was transmitted).
72 DH3 Packet This packet is similar to the DM3 packet, except that the information in the pay-load is not FEC encoded. DH3 packet can carry up to 185 information bytes (including the two bytes payload header) plus a 16-bit CRC code. The DH3 packet may cover three time slots. When a DH3 packet is sent or received, the hop frequency shall not change for a duration of three time slots (the first time slot being the slot where the channel access code was transmitted).
73 DM5 Packet The DM5 packet is a DM1 packet with an extended payload. The DM5 packet may cover up to five time slots. The payload contains up to 226 information bytes (including the 2-bytes payload header) plus a 16-bit CRC code. The pay-load header in the DM5 packet is 2 bytes long. The length indicator in the pay-load header specifies the number of user bytes (excluding payload header and the CRC code). When a DM5 packet is sent or received, the hop frequency shall not change for a duration of five time slots (the first time slot being the slot where the channel access code was transmitted).
74 DH5 Packet This packet is similar to the DM5 packet, except that the information in the pay-load is not FEC encoded. DH5 packet can carry up to 341 information bytes (including the two bytes payload header) plus a 16-bit CRC code. The DH5 packet may cover five time slots. When a DH5 packet is sent or received, the hop frequency shall not change for a duration of five time slots (the first time slot being the slot where the channel access code was transmitted).
75 AUX1 Packet This packet resembles a DH1 packet but has no CRC code. The AUX1 packet can carry up to 30 information bytes (including the 1-byte payload header). The AUX1 packet may cover up to a single time slot.
76 Packet Summary (1)
77 Packet Summary (2)
78 ISM Overhead ACL data packets 142 non-data bits (72b access code, 54b packet header, 16b CRC) DH5 packets in asymmetric transmission 5 slots 339 bytes = 2712 bits of data = 2854 bits transmitted in total 2712 bits / (6 * 625µs) = kb/s < 1Mb/s Necessary overhead to provide a robust link over the ISM band.
81 Logic Channels LC (Link Control) Carried out via the packet header LM (Link Manager) Typically carried by DM0 type packets with L_CH=11 DM1 is common to SCO and ACL, allowing LMP messages to be carried over an active SCO link UA / UI (User Asynchronous) Carried by ACL payload US (User Synchronous) Carried by SCO payload
82 Synchronization (1) TX Slot RX Slot Correlator open RX Timeout T Match
83 Synchronization (2) Start of packet header T Match + 1 µs for 68b access code T Match + 5 µs for 72b access code (with trailer) Offset from the Master = T Match - 68µs The updated CLKE and sub-slot count are applied immediately.
84 Link Control Chingwei Yeh 2001/9/10
85 Outline Link Control Protocol Link Controller States and Operations Master / Slave Role Switching Low-power Operation
86 Link Control Protocol Carried in the LC channel Responsible for maintaining a link once it has been set up
87 ARQN ARQN=0: previous receive failed Access code failure A Slave fails to detect an access code (not possible) A Master fails to detect an access code Header failure Slave side: an access code is detected but HEC fails (not possible due to corrupted AM_ADDR) Master side: an access code is detected but HEC fails Payload failure An access code is detected but CRC fails The usual reason for re-transmission during connection
88 SEQN SEQN Toggled each time a new packet with a CRC is transmitted Remains the same otherwise Used to differentiate receiver NAK d the previous packet transmitter failed to receive the receiver s ACK Same SEQN packet ignored, but ACK returned
89 ARQ/SEQ under Broadcast ARQ scheme is not applicable Re-transmit broadcast packets a specified number of times (N BC ) Each new broadcast packet in a sequence is identified by toggling SEQN Spec 1.0B resets SEQN upon each start of LMP and L2CAP?!
90 Link Controller States Standby Inquiry Inquiry Scan Page Page Scan Connection Active, Hold, Sniff, Park In Standby, Hold, Park the device may be driven by a LPO with ±250ppm.
91 Inquiry and Inquiry Scan
92 Inquiry (1) To discover all Bluetooth enabled devices in its local area Baseband end of the Service Discovery Protocol (SDP) May be initiated one-shot or periodically (HCI_Periodic_Inquiry_Mode) Inquired upon devices supply FHS CLKN, BD_ADDR, etc
93 Inquiry (2) A device in the inquiry substate does not acknowledge the inquiry response. It just keeps probing at different hop channels and in between listens for response packets. Stops when Instructed inquiryto
94 What to Inquire No knowledge of the environment No BD_ADDR, CLK, etc Both the inquirer and inquiry scanner uses the same hopping sequence determined by GIAC LAP Still can not communicate even the same hopping sequence is used
95 Inquiry Objective Objective: to capture the scanners as quickly as possible. Only need to match the frequency for one slot pair to allow information retrieval. Basic Concept Use the same hopping sequence The inquirer hops fast The inquiry scanners hop slow Eventually they will meet
96 The Hop of the Inquirer GIAC+CLKN(inquirer) the hopping sequence for inquiry. A train of identical GIACs at different hopping frequencies Frequencies in the train is designed to surround a central frequency Although it seems alright to use any sequence through the spectrum, the spec. aligned the inquiry sequence to that of the page.
97 Inquirer Fast Hopping TX transmits on two different hop frequencies. RX listens on two different hop frequencies. ID packet (68bits) (uncertainty) = 224.5us to switch the freq. synthesizer.
98 Inquiry Trains (1) A train of identical GIACs at different hopping frequencies. Frequencies in the train is designed to surround a central frequency The central frequency is determined by the hopping sequence. The hopping sequence is determined by the general inquiry address GIAC LAP + 4 LSBs of the DCI (pp. 137, pp. 54)
99 Inquiry Trains (2)
100 Inquiry Train A 16 different hop frequencies in 16 slots (10 ms) Train A f(k-8), f(k-7),,f(k),,f(k+7) Covers 8x1.28s to 7x1.28s deviation from CLKN(inquirer) 16 * 625µs = 10ms f(k) is one frequency in the hopping sequence, which is determined by CLKN (CLKN ) (changed every 1.28s, regardless of N inquiry 256)
101 Inquiry Train B 16 different hop frequencies in 16 slots (10 ms) Train B f(k-16), f(k-15),,f(k-9),f(k+8),f(k+15) Covers drifts from CLKN that are Less than 8*1.28s More than 7*1.28s f(k) is one frequency in the hopping sequence, which is determined by CLKN (CLKN ) (changed every 1.28s, regardless of N inquiry 256)
102 Inquiry Train Usage (1) N inquiry of train A N inquiry of train B N inquiry of train A N inquiry of train B (three train switches) N inquiry 256 Alternately use train A and B until A response is received inquiryto is exceeded
103 Inquiry Train Usage (2) Train A and B Each train is repeated at least N inquiry 256 times At least three train switches must be taken place So, inquiry substate lasts for at least 256*10ms*4=10.24s If inquiry is activated periodically, the interval between two inquiry instances must be determined randomly (avoiding inquiry synchrony, HCI_Periodic_Inquiry_Mode )
104 Inquiry Train Illustration 128*(16*625us)=1.28s 128 TA 128 TA 128 TB 128 TB 128 TA. 128TB N inquiry (=256) 3 train switches, 4*256*10ms = 10.24s 16*625us = 10ms
105 Entering Inquiry Inquiry can be entered from STANDBY CONNECTION Entering from connection Hold or Park ACL Interrupted by SCO increase scan window
106 Inquiry Scan (1) A device wanting to be discovered could conduct an inquiry scan until it has responded to an inquiry, then do a mandatory page scan. If that doesn t result in a connection, go back into inquiry scan. Battery, radio receiver power consumption Continuous scanning would cause existing connections to timeout So, scan in short bursts! Short bursts (18 slots,11.25ms), short interval ( 2.56s)
107 Inquiry Scan (2) Hop sequence is determined by GIAC. The phase is determined by CLKN of the scanner. Scan at a single hop frequency in 1.28s Hops every 1.28s Listen to GIAC/DIAC for at least 18 slots in T scan interval ( 2.56s in spec, and stay in discoverable mode for at least 30.72s
108 Entering Inquiry Scan Inquiry scan can be entered from STANDBY CONNECTION Entering from connection Hold or Park ACL Interrupted by SCO increase scan window
109 Inquiry Scan with SCO One SCO link(hv3, T SCO = 6 slots) T w inquiry scan at least 36 slots(22.5ms) Two SCO link(hv3, T SCO = 6 slots) T w inquiry scan at least 54 slots(33.75ms) The inquiry scan interval shall be at most 2.56s
110 SCO During Inquiry Scan = 50% waste if one SCO in every 3 slot pairs Correlator Opens For inquiry scan ±10us ID 625us Ratio Settle Time 150us 200us 366us FHS 2x625us Correlator Opens For inquiry scan RX Inquiry Scan Slot Pair Starts TX SCO Slot Pair Starts
111 Inquiry Response (1) Only slave responds (with FHS packet) Multiple devices may respond at the same time collision!
112 Inquiry Response (2) Response steps (to avoid collision) Received inquiry message RAND 0~1023 Memorize the phase in the hopping sequence Return to CONNECTION or STANDBY for at least RAND time slots inqrespto counter starts Listen for inquiry message with inqrespto, and if correctly received Return FHS (Master collects information now) Phase++ Return to inquiry scan
113 Inquiry Response (3) In 1.28s, the slave responds 4 times in average. (1.28s/625µs)/(RAND/2)=4
114 Page and Page Scan
115 Page To establish a connection, the Master is instructed by the application to carry out the paging procedure. Using the Slave s access code and timing information gathered previously. FHS packets in-between
116 What to Page The Master knows the device BD_ADDR (DAC) CLKE Need to make CLKE as precise as possible Both the pager and page scanner use the same hopping sequence determined by DAC LAP Still may not communicate properly even the same hopping sequence is used
117 Page Objective Objective: to capture the offset of phase as quickly as possible. Basic Concept Use the same hopping sequence (DAC) The pager hops fast The page scanner hops slow Eventually they will meet
118 The Hop of the Pager DAC+CLKE(pager) the hopping sequence for inquiry. A train of identical DACs at different hopping frequencies Frequencies in the train is designed to surround a central frequency CLKE(pager) Last encounter with the Slave (e.g., the previous inquiry)
119 Pager Fast Hopping TX transmits on two different hop frequencies. RX listens on two different hop frequencies. ID packet (68bits) (uncertainty) = 224.5us to switch the freq. synthesizer.
120 Paging Trains (1) A train of identical DACs at different hopping frequencies. Frequencies in the train is designed to surround a central frequency The central frequency is determined by the hopping sequence. The hopping sequence is determined by the DAC
121 Paging Trains (2)
122 Paging Train A 16 different hop frequencies in 16 slots (10 ms) Train A f(k-8), f(k-7),,f(k),,f(k+7) Covers 8*1.28s to 7*1.28s deviation from 16 * 625µs = 10ms CLKE(pager) f(k) is one frequency in the hopping sequence, which is determined by CLKE (pager) (CLKE (pager) in half-hop systems) Phase changed every 1.28s, regardless of N page
123 Paging Train B 16 different hop frequencies in 16 slots (10 ms) Train B f(k-16), f(k-15),,f(k-9),f(k+8),f(k+15) Covers drifts from CLKE(pager) that are Less than 8*1.28s More than 7*1.28s f(k) is one frequency in the hopping sequence, which is determined by CLKE (pager) (CLKE (pager) in half-hop systems) Phase changed every 1.28s, regardless of N page
124 Paging Train A & B Usage N page of train A N page of train B. Alternately use train A and B until Receive a response pageto is exceeded
125 Paging Train Illustration 128*(16*625us)=1.28s 128 TA 128TA 128 TB 128 TB 128 TA. 128TB N page (=256) (N page can be 1, 128, 256) Alternately use train A and B until a response is received or pageto 16*625us = 10ms
126 Page Modes R0: N page 1 (16 slots,16 slots ) Continuous, T w page scan = T page scan R1: N page 128 Once in a while T w page scan 18 slots T page scan 1.28s R2: N page 256.
127 Entering Page Page from STANDBY CONNECTION Entering from connection Hold or Park ACL Interrupted by SCO increase scan window
128 Paging with SCO (1)
129 Paging with SCO (2)
130 Paging Scheme Mandatory paging scheme First met Paging directly following inquiry Optional paging/scanning scheme After the mandatory scheme
131 Page Scan (1) Like inquiry scan, a device may enter page scan periodically to allow connection with it. When page scan completes, the Slave updates CLK, sync word, and access code before entering the connection state.
132 Page Scan (2) Can be entered from STANDBY CONNECTION Entering from connection Hold or Park ACL Interrupted by SCO increase scan window
133 Page Scan (3) Listen for its DAC for T w page scan 18 slots T page scan determined by SR (scan repetition) Hop sequence determined by the Slave s BD_ADDR. Phase in the hopping sequence is determined by CLKE (pager) (CLKE (pager) in half-hop systems) Phase changed every 1.28s, regardless of N page
134 Page Scan Repetition (SR) SR field in the FHS packet The paging unit must choose R0, R1, or R2 accordingly.
135 Page / Page Scan Modes R0: N page 1 (16 slots,16 slots ) Continuous, T w page scan = T page scan R1: N page 128 Once in a while T w page scan 18 slots T page scan 1.28s R2: N page 256.
136 Page Scan with SCO One SCO link(hv3, T SCO = 6 slots) T w page scan at least 36 slots(22.5ms) Two SCO link(hv3, T SCO = 6 slots) T w page scan at least 54 slots(33.75ms)
137 Page Response Procedure (1)
138 Page Response Procedure (2)
139 Page Response Procedure (3)
140 Slave Response The X input to hop sequence generator is fixed at CLKN The Slave awaits FHS within pagerespto Within pagerespto, the Slave advances to the next phase every 1.25ms to match with the Master s next paging frequency. After pagerespto Page scan for one additional scan period, if not successful, return to the state prior to page scan.
141 Master Response FHS packet Real-time Bluetooth clock (26 MSBs only), Master s BD_ADDR, BCH parity bits, etc (all information to construct the channel access code without requiring a math derivation from the Master s BD_ADDR) Repeat FHS with updated phase until either successful or pagerespto If failed, report to LM
142 Connection Confirmation On entry, both devices move to the pager s hop sequence. To verify the success of the link set-up The Master transmits a POLL packet which the Slave must respond (typically with NULL). Both ARQN=NAK (still a response!). If everything goes well Master transmits and starts ARQ, SEQ for real. LMP configuration starts. Master/Slave role switch can proceed, if desired.
143 Connection Time-out When both the Master and Slave switches to the Master s normal hopping sequence, newconnectionto (in terms of #slots) is ticked. If after newconnectionto, either POLL is not received by the Slave POLL response is not received by the Master then connection is regarded failed, and both return to the page and page scan states
144 Synchronization the Slave The Slave stays synchronized to the Master during a connection by correlating against the Master s access code (CAC) in each packet the Mater transmits, even if it s not destined for that Slave. If AM_ADDR does not match abort the remainder of the reception, and use packet type field to reduce power consumption for the duration of Master s transmission any device in connection state may move into Low Power mode as described above
145 Synchronization the Master The Master must keep transmitting periodically, even if there is no data to send. A NULL packet is usually used for this purpose.
146 Connection Active, Hold, Sniff, Park
147 Connection Modes Active Low-power Hold: Allows device to be inactive for a single short period. Sniff: Allows devices to be inactive except for periodic sniff slots. Park: Similar to Sniff, except parked devices give up their active member addresses.
148 Connection Active The Master schedules transmission based on traffic demands to and from different slaves. Constant Master transmission to keep synchronization (channel access code). If an active slave is not addressed, it may sleep until the next master transmission. Type of packet the number of slots
149 Connection Hold (1) A device ceases to support ACL for a negotiated period of time to free up bandwidth for other operations like Scanning, paging, inquiry. SCO is not affected. AM_ADDR is maintained. Re-synchronizes to CAC after holdto.
150 Connection Hold (2) HCI_Hold_Mode Connection Handle, Max/Min hold periods HCI_Write_Hold_Mode_Activity LMP_hold_req (1st or refresh) LMP_accepted, LMP_not_accepted LMP_hold_req (negotiating different parameters) LMP_hold (after the 1st hold)
151 Connection Sniff (1) The Slave is given a pre-defined slot time and periodicity to listen for traffic. The Master can only transmit at the specified time slots. Starting at every D sniff instant, repeat for N sniff attempt times. Master CLKN[27:1] mod T sniff = D sniff Master (CLKN, CLKN[26:1]) mod T Sniff = D sniff Received Master s call(s) within N sniff attempt continues listening for Sniff_Timeout
153 Connection Park Similar to Sniff, but the Slave gives up its AM_ADDR. Cannot transmit Cannot be addressed directly by the Master The Slave only needs to wake up at a defined Beacon instant to listen for broadcasts to synchronize.
154 Park Mode Purpose Low Power To accommodate more than 7 slaves Parked Slaves still synchronized to the channel Give up AM_ADDR and receive PM_ADDR  (Parked Member Address) AR_ADDR  (Access Request Address) Park only one slave at a time All messages sent to the parked Slaves must be carried by broadcast packets.
155 Beacon Instants and Slots (1) Transmission for synchronization of the parked devices Carrying messages to the parked devices to change the beacon parameters Carrying general broadcast messages to the parked devices Unparking of one or more parked devices
156 Beacon Instants and Slots (2) N B and T B are chosen so that there are sufficient beacon slots for a parked slave to synchronize. The Slave receives beacon parameters through an LMP command. CLK 27-1 mod T B = D B for initialization 1 (CLK 27, CLK 26-1 ) mode T B = D B for initialization 2 Any packet can be used for synchronization May be interrupted by SCO link
157 Beacon Access Window (1) Parked slaves send requests to be unparked Fixed delay D access after beacon instant Repeat M access times
158 Beacon Access Window (2) Parked Slaves can only respond if the Master has broadcast in the preceding even slot. Polling Wait for the Master to broadcast an unpark message.
159 Beacon Access Window (3)
160 Sleeping Through Beacon Slots Sleep window = N B_sleep * T B
161 Park Mode Addressing Master initiated unpark uses PM_ADDR BD_ADDR (All zero PM_ADDR is reserved for those that can only be unparked by BD_ADDR) Slave initiated unpark uses AR_ADDR
162 Entering Park Mode HCI_Park_Mode Connection_Handle, Max/Min interval between beacon slots LMP_park_req (a whole lot of parameters, see the spec) LMP_park, LMP_accepted, LMP_not_accepted LMP_set_broadcast_scan_window, LMP_modify_beacon
163 Master-Activated Unparking HCI_Exit_Park_Mode w/ connection handle. LMP_unpark broadcast in a beacon slot PM_ADDR or BD_ADDR A new AM_ADDR The Slave receives the unpark message returns to active mode. The Master POLLs with the new AM_ADDR. LMP_accepted to confirm the Slave has been unparked. newconnectionto Master : unpark the slave in the next beacon slot Slave : return to park with the same beacon parameters
164 Slave-Activated Unparking (1) Send an access request message in the access window only when a broadcast packet has been received. The message is an ID packet with Master s DAC Listen for Master s unpark message. If not, try in the next access window (total: M access windows). After the last access window, the Slave shall listen for N POLL slots for the unpark message. Fail sleep until the next beacon instant.
165 Slave-Activated Unparking (2) Unpark message received The Slave listens for POLL with its AM_ADDR, and then responds. If the Master did not receive response after N POLL + newconnectionto Master : send unpark message again Slave : return to park with the same beacon parameter
166 Polling Schemes Polling in active mode ACL: A slave is allowed to transmit in a slot only if it was addressed by the preceding slot. SCO: A slave is allowd to transmit unless the (valid) AM_ADDR in the preceding slot indicates a different slave. Polling in park mode A slave can only respond after a broadcast packet is received in the preceding slot.
167 Broadcast Scheme All-zero AM_ADDR New broadcast message shall start with the flush indication(l_ch=10) Never acknowledged no traffic at the beacon event broadcast packets shall be sent.
168 Scatternet Each piconet has their own channel hopping sequence and phase as determined by the respective Master. The packets are preceded by different channel access codes.
169 Inter-Piconet Communications ACL only Hold or park the current piconet connection, then Join the other piconet by changing channel parameters. Sniff mode : in between the sniff slots SCO In the non-reserved slots Four slots in between, two for misalignment Regular updates is necessary as the clocks of various piconets drift independently.
170 Master-Slave Switch Happens when slave wants to be a Master Redefinition of the piconet New piconet parameter
171 Master-Slave Switch Process (1) Slave A and master B agree to exchange roles (LMP) When confirmed, A & B do the TDD switch but keep the former hopping sequence. A now becomes the Master of the piconet
172 Master-Slave Switch Process (2) A now becomes the Master of the piconet The 1.25ms resolution in FHS is not enough to align the slot boundary A sends LMP packet giving the delay of the old and new master-to-slave slots (0 to 1249µs, resolution=1µs) After LMP time alignment, A sends FHS including the new AM_ADDR to B, still using the old piconet parameters After ACK (ID) by B, both A & B switch to the new channel parameters of the new piconet.
173 Master-Slave Switch Process (3) A piconet switch is enforced on each Slave separately. For each Slave, A sends a time alignment and FHS packets using old parameters. Upon ACK (ID), the Slave switches to the new parameters. The FHS sent to each Salve has the old AM_ADDR in the FHS packet header and their new AM_ADDR in the FHS packet payload. A polls each Slave to verify the swtich within newconnectionto. Repeat if verification failed.
174 Link Supervision Break down Out of range Power failure Supervision Timer (Master, Slave, SCO, ACL) Reset when access code & HEC & correct AM_ADDR is received supervisionto negotiated at LM level, longer than hold and sniff period Connection is reset when supervisionto expires
175 Link Controller States Revisited Major states Standby Connection Substates Page Page scan Inquiry Inquiry scan Master response Slave response Inquiry response
176 Complicated Context Switching The previous figure represents only the state of one link between two devices at any one time. A Master may be in connection with one Slave while simultaneously inquiring, paging, and scanning several other devices. Inquiry/paging may last for several seconds
177 HW/SW Partitioning Needs a unique context for the LC protocol, ARQN, SEQN, and re-transmit packets of an active interaction. The area of state control and link context management is at the sharp end of the hardware/software (HW/SW) partitioning problem.
178 Other Baseband Topics Left Hop Selection Algorithms Audio Error Corrections and Security Related Algorithms
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