Wireless topologies
Networks of this type function in one or more versions.
- Point to Point
A simple option for organizing a network consisting of a pair of devices. Provides bi-directional direct communication over dedicated channels without requiring a control system. The nodes of this network are usually peer-to-peer, that is, peers. The topology is used by Bluetooth, RFID, Wi-Fi, etc.
- Star
Carries out round-robin multi-directional traffic between the central station and remote terminals. The “star” topology is the basic option for organizing communication networks. It is used by UWB, Insteon, Wi-Fi, etc.
For note, to find the determinant of the matrix, you can easily get the calculation using an online determinant calculator.
- Multi-cell network
Fully connected base topology of communications networks, where each network workstation connects to other stations on the same network. Each node has several options for connecting to other nodes, which gives the topology additional resilience.
Typical for large networks, it is highly fault-tolerant, but at the same time difficult to configure, additional cable consumption in wired networks. Used by WiMAX, GSM, GPRS, etc.
- Cluster tree
Formed from combinations of the above topologies. The base of the “tree” is located at the point (“root”) where information communication lines (“branches”) are collected. Networks with a tree structure are used where it is impossible to apply basic topologies.
Access sharing methods
Such methods allow transferring significant amounts of information in a short time period, as well as maintaining communication with several users in narrow frequency ranges.
- CDMA
Expansion of several access technologies, which uses an innovative coding scheme that allows several subscribers to simultaneously exchange data over one physical channel. Each user group is given a unique shared code that is not available to other groups. This technology increases the number of signals for a given frequency band and is used for 3G telephony.
- CSMA
Probabilistic network protocol of the link layer. By transmitting a data packet, the node pre-estimates the channel purity (determines the noise level). If it's free, the node sends the packet. If there is another transmission on the channel, the node “drops” and waits before sending the packet again.
- TDMA
The main technology for mobile networks. The protocol is time-division multiple access. In this case, several subscribers are simultaneously in the same frequency interval, and different time intervals (slots) are defined for transmitting data to different users.
- OFDM
Acts as an application of GSM-frequency multiplexing in radio communications. The technology is represented by multiple access, where channels are allocated by frequency.
One user is in the same band, and different users use different frequencies within the cell. Until the initial request is completed, the channel remains closed to other communications.
Wireless security
Depends on the use of several technologies: digital signature, encryption, changing keys, passwords, etc. The degree of network security depends on their use.
Encryption algorithms
There are several encryption algorithms:
1. E0 – this stream cipher is used for the Bluetooth standard. Built on the basis of three linear shear generators;
2. AES – used to protect wireless data transmission channels in the ZigBee, UWB, RuBee, Wi-Fi, WiMAX protocols;
3. Rolling Code System – the cipher uses a recurrent linear shift register (main – 32 bits, additional – 5). Encryption is performed by bit-by-bit addition with a key;
4. Crypto 1 – a combination of non-linear and linear recurrent registers with a key length of 48 bits;
5. A5 – the data stream is encrypted bit by bit. There is a summation of the stream of information received over the radio channel from the user and the bitstream of the key generated by a similar algorithm.
