Comparison of near-distance communication technology and near-distance communication technology

Comparison of near-distance communication technology and near-distance communication technology

Comparison of near-distance communication technology

Compared with the traditional near-distance communication, near-field communication (NFC) provides natural security and fast connection establishment. The comparison is as follows:

 

Table 2.1 comparison of communication parameters

	NFC	Bluetooth	Infrared
Network Type	Point-to-Point	Single point to multiple points	Point-to-Point
Distance used	≤ 0.1	≤ 10	≤ 1
Speed	106 kbps	212 kbps	424 kbps
Creation Time	<0.1 s	<6 s	<0.5 s
Security	Yes, hardware implementation	Yes, software implementation	Not available, except for IRFM
Communication Mode	Active-active/passive	Active-active	Active-active
Cost	Low	Medium	Low

 

RFID:

RFID (radio frequency identification) is an automatic identification technology that uses radio waves for communication. The basic principle is to achieve automatic identification of tag items by means of electromagnetic coupling or inductance coupling between the reading head and labels attached to the object. Automatic Identification refers to the application of a certain identification device to automatically obtain the information of the identified item through the near activities between the identified item and the identification device, it is also a technology provided to the background computer processing system for subsequent processing.

 

Major RFID frequencies include 125 kHz, 134.2 kHz, 13.56 MHz, 860-960 MHz, 5.8 GHz, and GHz. RFID systems with different operating frequencies have different operating distances and different application fields. RFID systems with Low Frequency segments (LF, 125 kHz, 134.2 kHz) are mainly used for animal identification and factory data collection. RFID systems with high frequency (HF, 13.56 MHz) have mature technologies, it is widely used in access control and intelligent transportation. The LF and HF frequencies work in the inductance coupling mode, with a low working distance. The ultra-high frequency band (UHF, 860-960 MHz) the effective working distance of the RFID system electronic tag can reach 3-6 meters, suitable for logistics, supply chain and other fields. Microwave Frequencies (5.8 GHz and GHz) are used for container management and highway charging. The frequency bands of UHF and microwave frequencies work in electromagnetic coupling mode, and the working distance is far away.

 

NFC

Like RFID, NFC information is transmitted through electromagnetic induction coupling of Wireless frequencies in the spectrum. However, NFC uses a near-field magnetic field coupling (usually using a magnetic film to fit the FPC) antenna, the 13.56Mhz wavelength is used, and the read/write distance is very short. First, its transmission range is smaller than that of RFID, And the RFID transmission range can reach several meters or even dozens of meters. However, due to NFC's unique signal attenuation technology, compared with RFID, NFC is characterized by proximity, high bandwidth, and low energy consumption [12].

NFC is compatible with RFID technology. More RFID applications are used in production, logistics, tracking, and asset management, while NFC plays a huge role in access control, public transportation, mobile payment and other fields [13].

Compared with the traditional near-distance communication, Bluetooth and infrared, near-field communication (NFC) provides natural security and fast connection establishment. For example, see Table 2.1 ):

 

 

Bluetooth 4.0

Bluetooth 4.0 is different from the previous Bluetooth version that must have a sender and receiver. You can select three modes: only the transmitter mode, only the receiver mode, and the transceiver mode.

In terms of RF, the transmit power is controlled within the range of-20 dBm ≤ PAVG ≤ + 10 dBm EIRP (the antenna gain is assumed to be 0dBi), and there is no concept of Bluetooth power level, it is also 10 dB less than the definition of the previous classic Bluetooth maximum transmit power of 20 dBm, and the receiver sensitivity ≤-70dBm is 0.1% error rate. The working range can be larger than 10 meters, and only GFSK is used as the modulation method. The modulation index is between 0.45-0.55, and the frequency hopping mode is used. The transmission rate is 1 Mbps. There are 40 channels with 2 M bandwidth, which is doubled from the classic Bluetooth 1 M bandwidth. According to Shannon's law, at a certain transmission rate, you can increase the channel bandwidth to reduce the signal-to-noise ratio, which is also one of the reasons for Bluetooth 4.0 low power consumption. If the unit is 1, the transmit power of 15.4 + ZigBee is 0.6, and that of Bluetooth 4.0 is 0.1. In addition, three dedicated broadcast channels are used to reduce Bluetooth power consumption and enhance anti-interference performance. Therefore, Bluetooth 4.0 is also called low-consumption Bluetooth.

In terms of channel structure, two types of channels are used: Broadcast Channel and data channel. The broadcast channel uses a channel with a RF channel number of 2480, 39, and a frequency of,. As a fixed broadcast channel, the broadcast channel is used to send broadcast data to and establish connections between unconnected devices, remote devices are found, and the number of broadcast channels can be reduced according to the surrounding interference conditions when transmitting broadcast data, and frequency hopping can be performed on three broadcast channels, all devices share these three broadcast channels for broadcast data. Data channels use 37 channels as dynamic frequency hopping channels to send application data for registration, Data, response, and link termination. For Bluetooth 4.0 devices, the same physical channel is used during work. For this purpose, the receiver and sender must jump to the same physical channel at the same time.

 

Wireless 433 MHZ

The transmission feature of the wireless 433MHZ band is: 433MHZ is the application-free transmission and receiving frequency in our country. It can be directly used without management. It is highly anti-interference in The 433 band and supports various point-to-point features, A one-to-multiple-point wireless data communication method has the features of integration of transceiver, security isolation, installation isolation, simple use, high cost performance, stable and reliable, as long as the transmit power is large enough, no problem during long-distance transmission

The 315MHZ and 433MHZ are our country's application-free launch and reception frequencies, and the 10GE is an old product in the data transmission field. Its critical weakness is that the system has poor security and confidentiality and is vulnerable to attacks, deciphering; lagging communication technology, unreliable communication, and unstable system; crowded channels, extremely high environmental interference, walkie talkie, on-board communication equipment, and amateur communication equipment are all concentrated here, as a result, environmental interference is very high; short-term use may not be seen, and long-term use will inevitably appear; in addition, high power consumption, large volume of transmitters and antennas, some manufacturers have introduced it into the Smart Home System, however, due to its weak anti-interference capability, inconvenient networking, and moderate reliability, the application in smart home is far from satisfactory.

 

ZigBee

 

ZigBee is a short-distance, simple architecture, low-consumption power and low transmission rate wireless communication technology. Its transmission distance is about dozens of meters, and the free GHz and MHz frequencies are used, the transmission rate is 20 KB to 250 Kbps. The network architecture has the Master/Slave attribute and can achieve bidirectional communication.

ZigBee has the following features:

(1) power saving: due to the low transmission rate of ZigBee, the amount of data transmitted is also small, so the signal sending and receiving time is short. Secondly, in non-working mode, ZigBee is in sleep mode, the conversion time between the working and sleep modes is generally only 15 ms, while the device search time is 30 ms. Through the above method, ZigBee is very power-saving, and through the battery, ZigBee can be used for up to 6 months to 2 years.

(2) High Reliability: the MAC layer of ZigBee uses the talk-when-ready Collision Avoidance Mechanism, which is to deliver data immediately when there is a data transfer requirement, each sent data packet is received by the recipient and sent a confirmation message. If no confirmation message is received, a collision occurs and a message is sent again, this greatly improves the reliability of system information transmission.

(3) high scalability: A ZigBee network can contain up to 255 ZigBee network nodes, one of which is a Master device, and the other is a Slave device. If Network Coordinator is used, the total Network can reach a maximum of 6500 ZigBee Network nodes. In addition, each Network Coordinator can be connected to each other, and the total number of ZigBee Network nodes will be considerable.