1 Introduction
ZigBee is a two-way wireless communication technology with close range, low complexity, low power consumption, low data rate, and low cost. It is mainly suitable for automatic control, sensing, monitoring, and remote control. At the same time support geolocation function. The IEEE802.15.4 working group has defined an inexpensive low-rate wireless connection technology for fixed, portable, or mobile devices with extremely low complexity, cost, and power consumption. When the ZigBee Alliance formulated the ZigBee standard, it adopted IEEE802.15.4 as its physical layer and media access layer specifications. On the basis of it, ZigBee Alliance has formulated the data link layer (DLL), network layer (NWK) and application programming interface (API) specifications, and is responsible for high-level applications, testing and marketing.
Bluetooth is also a short-range wireless communication technology. Since the Bluetooth specification was released, it has been applied in more and more fields. Such as industrial automatic control, home automation, carrier-class audio transmission, PDA, mobile phones and PC peripherals.
In the relationship between ZigBee and Bluetooth, the ZigBee Alliance believes that ZigBee and Bluetooth are complementary to each other, rather than competing with each other. This article will analyze the two short-range wireless communication technologies ZigBee and Bluetooth around the two aspects of technology and market, proving that Bluetooth will face ZigBee technology competition in certain applications. Finally, suggestions are made for the application and development of ZigBee and Bluetooth.
2 System complexity
The system complexity of ZigBee is much smaller than that of Bluetooth. This can be seen from the reference model of their protocol stack (Figure 1). The ZigBee protocol stack is simple, relatively easy to implement, and requires less system resources. It is estimated that running ZigBee requires about 28Kb of system resources; the Bluetooth protocol stack is relatively complex, which requires about 250Kb of system resources. ZigBee defines two
Types of equipment: full-function device FFD (Ful FuncTIonal Device) and simplified function device RFD (Reduced FuncTIonal Device). The network is a master-slave structure. A network has a network coordinator (Coordinator) and up to 65535 slave devices. The network coordinator must be FFD, which is responsible for managing and maintaining the network, including routing, security, node attachment and departure, etc. Only one network coordinator is needed for a network, and other terminal devices can be RFD or FFD. The price of RFD is much cheaper than FFD, and it occupies only 4Kb of system resources, so the overall cost of the network is relatively low. From this point of view, ZigBee is very suitable for networks with a large number of terminal devices, such as sensor networks and building automation.
3 Security
ZigBee uses a hierarchical security strategy: no security, access control list, 32-bit AES and 128-bit AES. If the system is used in a scenario with low security requirements, you can choose lower-level security measures in exchange for lowering system cost and power consumption; conversely, in application scenarios with high security requirements (such as military), you can choose Higher security level. such,
Manufacturers can take into account factors such as power consumption, system processing power, cost, and application environment to adopt appropriate security levels. ZlgBee adopted security strategies at the MAC layer and NWK layer respectively. When the data arrives at the destination after one hop, ZigBee only uses the security mechanism provided by the MAC layer; when in the case of multiple hops, ZigBee relies on high layers to ensure security. The security of the MAC layer and the NWK layer is described below.
The MAC layer security suite (Security Suites) is based on the following three operation modes: AES encryption in counter (CTR, Counter) mode, data integrity in cipher block chaining mode (CBC-MAC, CiPher Block Chaining), CTR and CBC-MAC phase Combined encryption and integrity (OW does CCM mode). The AES encryption algorithm at the MAC layer can protect the confidentiality, integrity, and authenticity of MAC commands, beacons, information frames, and response frames. The MAC frame header has a bit to indicate whether the MAC frame is encrypted. Each key is only associated with one security suite. In order to ensure data integrity, the MAC layer calculates the header and payload data to obtain a message integrity code (MIC, Message Integrity Code) with a length of 4, 8 or
16 bytes. At the same time, there is also a frame number in each MAC frame header to prevent frame loss and frame retransmission. The establishment of the key, the selection of the secure operation mode and the control of the processing process are the responsibility of the senior management.
The NWK layer also uses AES, and its security suite is based on the CCM * operating mode. CCM * includes all CCM functions, while providing only encryption and integrity only functions. Using CCM * allows a single key to be used in different security suites. Therefore, a key does not only belong to a single security suite, a high-level application can flexibly specify the security suite used by NWK. The NWK layer is responsible for security processing, but the control of the processing process is realized by the upper layer by establishing a key and deciding which CCM * security suite to use. In addition, the frame number and MIC can also be added to the NWK frame.
The Bluetooth protocol defines the security algorithms and processing procedures required for device authentication and link data stream encryption at the baseband. Device authentication is mandatory, all Bluetooth devices support the authentication process, and link encryption is optional. The authentication process of the Bluetooth device is based on the challenge-response mode and the shared encryption method. In order to make the data stream of the Bluetooth link concealed, a 1-bit stream cipher can be used to encrypt the link. The key size changes with each baseband packet data unit (BB-PDU) transmission. The encryption key can be obtained from authenticating the device. This means that before link encryption is used, at least one authentication has been performed between the two devices. The maximum length of the key is 128 bits.
From the above analysis, it can be seen that ZigBee and Bluetooth can guarantee security to a certain extent. But ZigBee is more flexible than Bluetooth, which is more conducive to control system cost.
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