It’s always great to know things inside out and clearly see design intent behind the scenes. When you have 20 years of experience in the Mobile Networks domain, you can explain things in a simple clearly understood way, and suggest some insights and ideas on how this information can be used.
Probably it’s the most comprehensive approach to share information within 5 short self-explanatory videos on our Platform.
Information Started and Aggregated into Several Videos
The 1st one starts with a historical perspective. It gives a better clarity of how ideas to implement ways to communicate with each other over a long distance came to life. Eventually in the form without using any wires and therefore not being connected to any specific place during conversation.
It will be needed to stress out mandatory components for networks to be considered as mobile networks – telephone service, automatic switching systems, seamless communication. Telephone service allows us to send human speech instantly over a long distance, which was never done before.
Establishing a connection between any two telephones out of a large group of telephones was named switching (or simply connecting). Switching mechanisms allow us to connect telephones certainly, rapidly and economically. A pair of wires extends from each phone to switching equipment in the telephone central office, where switching is done electronically, similar to the specialized work of a huge computer focused on switching only.
Seamless communication means that the user (holding a mobile device) geographically moves, but still can continue receiving service (e.g., voice call) without interruption.
It’s also great to discuss the Evolution of Mobile networks over time with a focus on end-user services, which are provided to customers.
Generations Of Mobile Networks
- 1st Generation networks were focused on Voice services and surrounded supplementary services (for example voice conference call between more than 2 subscribers).
- 2nd Generation networks introduced SMS (short message service) and data transmission services (which was never done before using mobile phones).
- 3rd Generation networks improved download packet data throughput up to 14Mbps and even higher. That also consequently enabled video call service of a good quality using mobile phones.
- 4th Generation networks were designed as pure packet data networks; even voice calls in 4G networks were implemented with packet data transmission technologies. End users could download with speeds up to nearly ~300Mbps.
- 5th Generation network improvements include significantly faster packet data rates. Data speed is expected to be up to 2 gigabits per second at the beginning and is planned to grow to even 100Gbps. Another improvement – higher connection density (including so-called Massive Machine Type Communication between millions of devices).
Another chapter with insights is about the evolution of radio resources, this is the ‘last mile’ of communication between mobile phones and base stations of mobile network operators.
Historically it was the slowest segment (bottleneck). So improving throughput through radio resources was a very important task. Several important aspects contributed to this task.
Radio Channel Bandwidth and Frequency in Mobile Networks
Radio channel bandwidth is the 1st component. What is it? You need to be familiar with the term frequency: radio waves make a certain amount of swinging (also named oscillation) per second while traveling from a source generating this wave. Number of such cycles per second is named as frequency.
When we need to send data over the air, we need to use not precise frequency, but actually frequency intervals, like a small slice with a range of frequencies. And range of frequencies represents such radio-channel bandwidth. The main idea is: that the wider the radio-channel bandwidth, the higher the data throughput could be potentially achieved. This comes from NY Quist’s theorem about sampling of digital signals.
Advanced Resource Allocation Techniques in Mobile Networks
Another effective resource allocation – possibility to multiplex (use at the same time) several sub-channels per single mobile phone. Special technologies for resource allocation could be used for that: FDMA (Frequency Division Multiple Access), TDMA (Time division multiply access), WCDMA (Wideband Code Division Multiple Access), or OFDMA (Orthogonal frequency-division multiple access).
They are about different physical possibilities to combine multiple channels – either using channels of different frequencies at a time, or from different times, or using special mathematical codes utilizing the physical phenomenon of sending signals over the air.
 The more resources are combined (each with its own bandwidth), the higher throughput can be achieved for end user.
Signal Modulation, Carrier Aggregation, and MIMO
Signal modulation allows to increase throughput even more. It can be compared with information archiving by computers. It’s done by using special modulations, which allow to sending of several bits per tact, which in turn increases overall end-user data throughput. Term bit (binary digit) is about the minimal information piece to be sent, and tact is the minimal equal time interval, during which information is to be sent.
There are the following names of modulations being used in Mobile Networks: QPSK, 16-QAM, 256 QAM, and 1024-QAM, allowing to send 2, 4, 8, 10 bits per tact respectively. There could be some others.
Carrier aggregation gives more boost, whereas carrier stands for a radio channel with wide bandwidth. In 4G LTE radio up to 5 carriers with 20 MHz each could be aggregated for one end user.
MIMO was the next technique allowing the simultaneous use of up to 4×4 antennas (on both the transmitting and receiving sides). It helps with interference and also allows for increased data throughput when different signals are sent through different antennas. Massive MIMO with large antenna arrays, beam forming, and beam steering techniques were the next improvement, which can be seen in 5G networks.
I also want to strengthen that all these items may be used in combination: we can have very large radio channel bandwidth on 4G and 5G radios, and at the same time we can multiplex resources within your resources allocation technique, like OFDMA; we can use advanced modulation, like 256QAM to increase throughput several times on the top of that; we can use MIMO in 4G or massive MIMO in 5G, which also can improve end-user throughput.
The very next chapter explains, which network functions (nodes) may be found inside Mobile Networks. It’s easier to consider 3 big subsystems: UE (User Equipment, e.g., mobile phone), RAN (Radio Access Network, where base stations are located, and CN (Core Network).
Core Network
Mobile Core Network is in the main focus for now and contains multiple Nodes, where each Node handles specific functionality. There are Databases with subscribers’ data; e.g., HSS (Home Subscribers Server) in 4G; and UDR (User Data Repository) in 5G.
And there are Nodes for implementing services. There is Mobility Management functionality to take care of tracking the location and state of UEs. There is Session Management functionality to create so-called Bearers for sending User Traffic.
Another chapter to share some extra insights and intriguing improvements with Mobile Networks, for example introduction of Unified IP-based protocol, currently widely used in Mobile networks; Voice over IP functionality; Automatic network parts configuration; Virtualization of nodes (Software running on Standard hardware-off-the-shelf); and others.
