©F.M. Rietti Radio Wave Communication Fundamentals

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 2 Radio Wave Communication –Wi-Fi Wi-Fi (or WiFi) is a local area wireless computer networking technology that allows electronic devices to connect to the network, mainly using the 2.4 gigahertz (12 cm) UHF and 5 gigahertz (6 cm) SHF ISM radio bands. The Wi-Fi Alliance defines Wi-Fi as any "wireless local area network" (WLAN) product based on the Institute of Electrical and Electronics Engineers' (IEEE) standards. However, the term "Wi-Fi" is used in general English as a synonym for "WLAN" since most modern WLANs are based on these standards. "Wi-Fi" is a trademark of the Wi-Fi Alliance. Follow this link about Wi-Fi Spectrum & channelsUHFWi-Fi AllianceInstitute of Electrical and Electronics Engineers standardsWLANlink –Not in all countries we have same channels

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 3 Radio Wave Communication (cont) Wi-Fi (cont) –Service set identifier (SSID) In addition to running on different channels, multiple Wi-Fi networks can share channels. A service set is the set of all the devices associated with a particular Wi-Fi network. Each service set has an associated identifier, the Service Set Identifier (SSID), which consists of 32 bytes that identifies the particular network. The SSID is configured within the devices that are considered part of the network, and it is transmitted in the packets. Receivers ignore wireless packets from other networks with a different SSID.

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 4 Radio Wave Communication (cont) Wi-Fi (cont) Securing methods A common measure to deter unauthorized users involves hiding the access point's name by disabling the SSID broadcast. While effective against the casual user, it is ineffective as a security method because the SSID is broadcast in the clear in response to a client SSID query. Another method is to only allow computers with known MAC addresses to join the network, but determined eavesdroppers may be able to join the network by spoofing an authorized address. Wired Equivalent Privacy (WEP) encryption was designed to protect against casual snooping but it is no longer considered secure. Tools such as AirSnort or Aircrack- ng can quickly recover WEP encryption keys. Because of WEP's weakness the Wi-Fi Alliance approved Wi-Fi Protected Access (WPA) which uses TKIP. WPA was specifically designed to work with older equipment usually through a firmware upgrade. Though more secure than WEP, WPA has known vulnerabilities. The more secure WPA2 using Advanced Encryption Standard was introduced in 2004 and is supported by most new Wi-Fi devices. WPA2 is fully compatible with WPASSIDMAC addressesspoofing Wired Equivalent PrivacyAirSnortAircrack- ngWi-Fi AllianceWi-Fi Protected AccessTKIPWPA2Advanced Encryption Standard

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 5 Radio Wave Communication (cont) Wi-Fi (cont) Using in Embedded Systems At this link Arduino Wi-Fi library as examplelink Wi-Fi chips –MicrochipMicrochip –TITI

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 6 Radio Wave Communication (cont) Bluetooth Bluetooth is a wireless technology standard for exchanging data over short distances (using short-wavelength UHF radio waves in the ISM band from 2.4 to GHz) from fixed and mobile devices, and building personal area networks (PANs). Invented by telecom vendor Ericsson in 1994, it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization. Bluetooth is managed by the Bluetooth Special Interest Group (SIG), which has more than 25,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics. The IEEE standardized Bluetooth as IEEE , but no longer maintains the standard.EricssonRS-232Bluetooth Special Interest Group

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 7 Radio Wave Communication (cont) Bluetooth (cont) Bluetooth operates at frequencies between 2402 and 2480 MHz, or 2400 and MHz including guard bands 2 MHz wide at the bottom end and 3.5 MHz wide at the top. This is in the globally unlicensed (but not unregulated) Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio frequency band. Bluetooth uses a radio technology called frequency-hopping spread spectrum. Bluetooth divides transmitted data into packets, and transmits each packet on one of 79 designated Bluetooth channels. Each channel has a bandwidth of 1 MHz. It usually performs 1600 hops per second, with Adaptive Frequency-Hopping (AFH) enabled.guard bandsfrequency-hopping spread spectrumAdaptive Frequency-Hopping

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 8 Radio Wave Communication (cont) Bluetooth (cont) –Communication and connection A master Bluetooth device can communicate with a maximum of seven devices in a piconet, though not all devices reach this maximum. The devices can switch roles, by agreement, and the slave can become the master (for example, a headset initiating a connection to a phone necessarily begins as master—as initiator of the connection—but may subsequently operate as slave). The Bluetooth Core Specification provides for the connection of two or more piconets to form a scatternet, in which certain devices simultaneously play the master role in one piconet and the slave role in another. At any given time, data can be transferred between the master and one other device. The master chooses which slave device to address; typically, it switches rapidly from one device to another in a round-robin fashion. Since it is the master that chooses which slave to address, whereas a slave is (in theory) supposed to listen in each receive slot, being a master is a lighter burden than being a slave. Being a master of seven slaves is possible; being a slave of more than one master is difficult. Complete specification at this linkscatternetround-robinlink

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 9 Radio Wave Communication (cont) Bluetooth (cont) –Bluetooth profiles In order to use Bluetooth technology, a device must be compatible with the subset of Bluetooth profiles necessary to use the desired services. A Bluetooth profile is a specification regarding an aspect of Bluetooth-based wireless communication between devices. It resides on top of the Bluetooth Core Specification and (optionally) additional protocols. –Details on profiles can be found herehere

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 10 Radio Wave Communication (cont) Bluetooth (cont) –Bluetooth using in Embedded Bluetooth can be used in embedded systems via shield card or BT dedicated IC. Soft Commands from IC to microcontroller depends from IC; for HT-05 shield a list can be found herehere

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 11

©F.M. Rietti LM-18 Computer Science SSI Embedded Systems I 12 Bluetooth (cont) Bluetooth profiles