2018

802.15.x Wireless

Technologies

ASSUMPTIONS FOR USING THIS TEACHING MATERIAL

DSR and OTSL takes no responsibility about the problem

which occurs as a result of applying the technical

information written in this document in a commercial

product, although the information is based on actual

implementation and our experiences, is reliable enough.

AGENDA

Networking basics

Wireless communication

Bluetooth

Coexistence in wireless networks

LAYERED ARCHITECTURE

ISO/OSI REFERENCE MODEL

Layer Unit Function 7. Application data High-level APIs

6. Presentation data Data format conversion / encryption

5. Session data Managing communication sessions

4. Transport segment Reliable transmission

3. Network packet Local addressing, routing, traffic control

2. Data Link frame Physical addressing, error detection (Medium Access Layer and Logical Link Control sub-layers)

1. Physical Link bit Transmission and reception of raw bit streams

HEADERS ENCAPSULATION

TCP/IP

Ethernet, 802.11, …

IP

TCP, UDP, …

HTTP, DNS, …

BASIC NETWORK TOPOLOGIES

Bus Star Ring

Tree Full mesh Partial mesh

ADDRESSING METHODS

Unicast (one-to-one)

Broadcast (one-to-all)

Multicast (one-to-many)

Anycast (one-to-one-of-many)

Geocast

2018

Wireless

communication

RADIO FREQUENCY

RF stands for Radio Frequency, but is often used in the sense for anything related with EM signals.

Electromagnetic radiation consists of electromagnetic waves, whose main characteristics are frequency, amplitude, and phase.

RADIO FREQUENCY

MODULATION

Modulation is the process of varying one or more properties of a periodic waveform with a modulating signal.

Carrier signal – the one being modulated.

Modulating signal conveys information.

AMPLITUDE AND FREQUENCY MODULATION

DIGITAL MODULATION EXAMPLES

FSK (Frequency-shift keying) two frequencies, representing 0 and 1

PSK (Phase-shift keying) two phases, representing 0 and 1

POWER

Electromagnetic waves transmit energy. Thus, we may speak about power (measured in Watts) transfer.

Power is often expressed using decibels.

Decibel: The decibel (abbreviated as dB) is a logarithmic expression of the ratio between the power, voltage, or current of two signals.

P = 10*lg(P2/P1) or P = 20*lg(E2/E1)

POWER

If we take some reference power, decibels can be used as an absolute measure.

For power, the most common reference is 1 mW.

Such power units are abbreviated as dBm (decibel-milliwats).

0 dBm = 1 mW 10 dBm = 10 mW 20 dBm = 100 mW

EXAMPLES

60 dBm = 1 kW – microwave oven radiation

27 dBm = 500 mW – typical mobile phone

15 dBm = 32 mW – typical WLAN transmission power

7 dBm = 5 mW – laser in a CD-ROM drive

0 dBm = 1 mW – Bluetooth class 3

-127 dBm = 178*10^-18 W – received power from GPS

LQI & RSSI

These are two frequently used signal metrics:

Received Signal Strength – the power of a received signal, in dBm units.

Link Quality Indicator – estimates how easily a received signal can be demodulated.

RSSI and LQI are completely independent of each other.

RADIO SPECTRUM

LONGER AND SHORTER WAVES

Longer waves

Shorter antennas

Better penetration

Lower data rate

Lower attenuation

Shorter waves

Longer antennas

Worse penetration

Higher data rate

Higher attenuation

MULTIPATH PROPAGATION

NARROWBAND AND WIDEBAND COMMUNICATION

NARROWBAND AND WIDEBAND COMMUNICATION

Wideband:

Faster communication

Harder to send and detect

Usually higher frequencies

Narrowband

• Slower communication

• Better sensitivity and range

• Usually lower frequencies

SIGNAL SPREADING

Shannon and Hartley channel-capacity theorem:

C = B × log2 (1 + S/N)

where C is channel capacity in bps, B is the channel bandwidth (Hz) and S/N is signal-to-noise power ratio.

Increasing signal power leads to higher channel capacity.

Increasing bandwidth leads to higher channel capacity.

SIGNAL SPREADING (CONT.)

C = B × log2 (1 + S/N)

The equation allows for the channel to have arbitrary capacity even if S/N is low (even below 1).

For that we need to perform the signal-spreading operation. Two most popular methods: FHSS and DSSS.

Process gain – ratio of spread, in dB.

SIGNAL SPREADING: FHSS

Frequency-Hopping Spread Spectrum

The carrier hops from frequency to frequency over a wide band.

SIGNAL SPREADING: DSSS

Direct Sequence Spread Spectrum

Each symbol is replaced by corresponding PN-sequence (larger in size). As a result, the signal frequency (and, therefore, signal bandwidth) increases.

A pulse of these frequencies is called a chip, and the new frequency is called chip rate.

Spreading Factor = chip rate / symbol rate

ADVANTAGES OF SIGNAL SPREADING

Lowered susceptibility to multipath fading

Longer operating distance

Harder to jam and detect

Inherent security

SIGNAL SPREADING: FHSS VS. DSSS

FREQUENCY ALLOCATION

Frequency allocation is the division of the EM spectrum into radio frequency bands.

Frequency allocation is regulated by governments.

International Telecommunication Union (ITU) coordinates the global use of the radio spectrum.

ISM BANDS

ISM (Industrial, Scientific, Medical) bands were originally reserved for purposes other than telecommunication.

Industrial heaters and microwave ovens.

Nowadays ISM bands are also actively used for short-range wireless communication.

ISM bands do not require licensing, but there are strict limitations on transmission power.

ISM BANDS

Some examples:

863-870 MHz (Europe only)

902-928 MHz (USA only)

2400-2500 MHz (worldwide)

5725-5825 MHz

WIRELESS NETWORKS

Type Distance Examples

WWAN up to 35 km GSM, 3G, etc.

WMAN up to 10 km WiMAX

WLAN up to 100 m Wi-Fi

WPAN ~ 10m Bluetooth, Zigbee, etc.

WPAN

Short-range communication (“Personal operating space”, POS).

Low cost, low power consumption, small size devices.

Objectives:

Getting rid of cable connections.

Interoperability.

Little or no infrastructure.

IEEE

IEEE = Institute of Electrical and Electronics Engineers is a professional association.

Among other things, this organization develops global standards in a broad range of industries.

IEEE 802.15 is a family of standards for wireless PANs:

802.15.1 – Bluetooth … 802.15.4 – Zigbee …

2018

Bluetooth

BLUETOOTH

A number of companies were looking to standardize the industry around a short-range radio link.

• Intel started a program called Business-RF;

• Ericsson had a program called MC-Link;

• Nokia had a program called Low Power RF.

They first met in 1996, and in 1998 the Bluetooth SIG (Special Interest Group) was founded.

It adopted the code name as a tribute to the tenth-century Viking king Harald Gormsson who peacefully united Denmark and Norway, whose nickname was "Bluetooth.”

BLUETOOTH

Bluetooth is based on RF data transmission.

Bluetooth operates in the 2.4 GHz ISM band.

Communication range is 10-100m

Low power consumption

Open and royalty-free specification

BLUETOOTH VERSIONS

V1.0b and 1.1 (1998) Basic architecture, radio spec, basic protocols.

V1.2 (2002) Faster connection, coexistence with WLAN, improved QoS (quality of service),

improved voice quality, data rate up to 1 Mbit/s.

V2.0+EDR V2.1+EDR (Enhanced data rate) (2004-2007) Faster data transfer: up to 2.18 Mbit/s (user data rate).

V3.0+HS (High speed) (2009) Power Optimization, improved security, enhanced power control, lower

latency rates, data rate up to 24 Mbit/s.

V4.0+LE (low energy) (2010) Lower energy consumption

V4.1 (2013) and V4.2 (2014) Multi roles support, improved Link layer privacy, IPV6 support, LTE co-

existence.

PICONET

Piconet is a collection of slaves operating with one master.

There can be up to 7 active slave devices.

BLUETOOTH LINKS

SCO (Synchronous Connection-Oriented) – used for 64kbit full-duplex voice data. The data is streamed instead of framed.

ACL (Asynchronous Connection-Less) – used for general data packets

BLUETOOTH CHANNELS

Bluetooth operates within 2402 MHz – 2480 MHz.

There are 79 channels, they are spaced 1 MHz apart.

BLUETOOTH FREQUENCY HOPPING

Bluetooth employs frequency hopping spread spectrum (FHSS)

The frequency is changed 1600 times a second.

The hopping sequence is determined by the Bluetooth address of the master.

Newer Bluetooth employ adaptive FHSS.

BLUETOOTH PROTOCOL STACK

BLUETOOTH PROTOCOL STACK (CONT.)

Radio

It is the layer where actual communication takes place.

Baseband / Link Controller

Constructing and decoding packets, encoding and error detection, controlling the radio, managing synchronization.

Link Manager Protocol

Establishing and managing links, authentication, pairing, handling power modes.

Host Controller Interface (HCI):

The HCI provides a command interface to the baseband controller and link manager, and access to hardware status and control registers. Essentially, this interface provides a uniform method of accessing the Bluetooth baseband capabilities.

BLUETOOTH PROTOCOL STACK (CONT.)

Logical Link Control and Adaptation Protocol (L2CAP):

Multiplexing – mixing messages from different senders before transmitting in order to achieve high throughput.

Segmentation and Reassembly – breaking input data into pieces at one end and conjoining at receiving end.

QoS – Quality of Service needed for that application.

RFCOMM Protocol:

The RFCOMM protocol provides emulation of serial ports over the L2CAP protocol. The protocol is based on the ETSI standard TS 07.10.

Service Discovery Protocol (SDP):

The service discovery protocol (SDP) provides a means for applications to discover which services are available and to determine the characteristics of those available services.

BLUETOOTH AND ISO/OSI

BLUETOOTH PROFILES

The Bluetooth SIG states, "Bluetooth profiles are general behaviors through which Bluetooth enabled devices communicate with other devices."

At a minimum, each profile specification contains information on the following topics:

Dependencies on other formats

Suggested user interface formats

Specific parts of the Bluetooth protocol stack used by the profile.

BLUETOOTH PROFILE EXAMPLES

File Transfer – allows to access the filesystem of another device.

Hands-Free Audio – allows to transmit voice-quality audio, uses SCO links.

Advanced Audio Distribution – for high-quality audio, uses L2CAP connections

Serial Port Profile – allows RFCOMM connections to be treated as serial cable connections.

WIRELESS COMMUNICATION TECHNOLOGIES

2018

Wireless

coexistence

WIRELESS COEXISTENCE

COEXISTENCE MECHANISMS

WLAN

WPAN

WLAN

WPAN

physical unit

wired connection

Implemented in one

physical unit and

communicating with each

other by wired connection

Implemented in different

physical unit and not

communicating with each

other by wired connection

Collaborative Non-collaborative

COEXISTENCE MECHANISM EXAMPLES

① AWMA : Alternating wireless medium access collaborative

② PTA : Packet traffic arbitration collaborative

③ DIS : Deterministic interference suppression collaborative

④ AIS : Adaptive interference suppression non-collaborative

⑤ APS : Adaptive packet selection non-collaborative

⑥ PS-ACL : Packet scheduling for ACL links non-collaborative

⑦ PS-SCO : Packet scheduling for SCO links non-collaborative

⑧ AFH : Adaptive frequency-hopping non-collaborative

COLLABORATIVE EXAMPLES

1. AWMA

2. PTA

3. DIS

WLAN time WPAN time WLAN time

time

TDMA (Time Division Multiple Access)

WLAN PTA

Controll Entity

WPAN

TxRequest TxRequest

TxConfirm TxConfirm

Status Status

transversal filter

This is effective for mitigating interference, but it deteriorates voice streaming such as SCO.

This can avoid deterioration of voice streaming by giving increased priority to SCO. But ACL data transfer rate will decrease.

input output

(the same principle as noise and echo canceller)

This is effective for mitigating interference, but it needs high cost and much time for implementation.

Approximating the contribution of interference sources and removing them

Fig.-6 PTA image

NON-COLLABORATIVE EXAMPLES

4. AIS

5. APS

Adaptive filter Delay

Σ

Cancelling the interference signal by the prediction signal

RLSL filter

Throughput in application

HV1 HV2 HV3 ＞ ＞

DM1 DM3 DM5 ＞ ＞

less influence of interference

more influence of interference

Selecting the packet type adaptively for the system that needs transfer rate

x(n)

y(n)

e(n) Approximation of the IEEE802.11 signal

IEEE802.15.1 SCO packet type

IEEE802.15.1 ACL packet type

Prediction unwanted narrowband IEEE802.15.1 signal

NON-COLLABORATIVE EXAMPLES (CONT.)

7. PS-SCO

8. AFH

packet to transmit

last Slave Rx : bad last Master Rx : bad

Slave Rx now : good Master Rx now : good

delay

This is the Adaptive Frequency Hopping in Bluetooth standard itself.

This method is used only for SCO transportation.

The packet type is converted from HV3 to EV1, and if the last frequency status of the starting packet slot is “bad,” the transmit packet is delayed until the start packet slot whose last frequency status is “good” is reached.

6. PS-ACL If the last frequency status of the packet slot is “bad,” the transmit packet is delayed until the packet slot whose last frequency status is “good” is reached.

METHODS OF IMPLEMENTING SUCH SYSTEMS

Devices from the same silicon manufacturer with collaborative mechanism

Implement system by using the WLAN device and Bluetooth device from the same silicon manufacturer and by using collaborative mechanism.

Devices from different silicon manufacturers with non-collaborative mechanism

Implement system by using the WLAN device and Bluetooth device from different silicon manufacturers and by using non-collaborative mechanism.

Combo device of WLAN and Bluetooth

Implement system by using one-chip system of WLAN subsystem and Bluetooth subsystem designed recently by major silicon manufacturer (such as CSR, Broadcom, Texas Instruments, etc.), and by using collaborative mechanism.

DEVICES FROM THE SAME SILICON MANUFACTURER

High reliability in behavior of collaborative mechanism, because of devices from the same silicon manufacturer. Considerations: • At the master device, use AWMA and PTA as a core method; DIS and AFH as selectable options. • It is necessary to control dynamically the enable/disable of AWMA, configuration of WLAN/BT time

length, and configuration of PTA priority, according to usage scene of application. • At the slave device (such as a BT mobile phone, Wi-Fi PDA, etc.), select AIS as an option when there

is strong interference between WLAN and Bluetooth. • There is a selectable antenna option that is a WLAN/BT independent type or a WLAN/BT shared type

WLAN

BT

AWMA PTA

AIS DIS

BT mobile

phone

AIS

shared

antenna

independent

antenna

master device

WLAN AP

In this collaborative mechanism,

collision of only the Tx packet

can be avoided.

In the case that the WLAN Rx

packet reaches a shared antenna

when Bluetooth is transmitting

the packet in WPAN time, WLAN

loses this Rx packet.

Collaborative mechanism

required

optional

DEVICES FROM DIFFERENT SILICON MANUFACTURERS

If the performance of the WLAN device or PTA algorithm from the same silicon manufacturer do not meet the requirement of the application, the WLAN device from the other silicon manufacturer is selected and AFH runs on Bluetooth.

AFH can meet the basic coexistence mechanism, and there is a merit that the devices from different silicon manufacturers can be selected.

Because the situation that hopping table is WLAN in-band can be avoided by AFH, the interference can be avoided almost perfectly by only the non-collaborative mechanism.

Because Bluetooth application and Wi-Fi application can be run independently, it becomes easy to reuse the past resources of Bluetooth and Wi-Fi.

WLAN

BT

AFH

AIS

AIS

independent

antenna

WLAN AP master device slave device

Collaborative mechanism

required

optional

COMBO DEVICE OF WLAN AND BLUETOOTH

Features:

Major silicon manufacturers such as CSR, Broadcom, Texas Instruments, etc., have released the one-chip device that includes WLAN, Bluetooth, GPS, FM and so on.

The device of each silicon manufacturer includes IEEE802.15.2 Part 15.2 collaborative algorithm. And each silicon manufacturer adds their own coexistence mechanisms:

For example, in the Broadcom device, the function is added that the device transmits to AP the packet that notifies that the device cannot receive the Rx packet, and avoids packet-loss by making Rx packet retained in the AP. A function is added that reduces battery consumption and reduces noise by power-down.

Each silicon manufacturer designs ICs for target application so users can select ICs for their specific application.

Consideration for implementation:

PTA logic varies by each silicon manufacturer and each target application. It is important to check the design concept of PTA logic in selection to achieve expected performance.