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The Internet of Things is the key technology that determines the future of the economy. The ubiquitous Internet of Everything will eventually become a reality.
However, the ubiquitous IoT coverage is not that easy.
Internet of Things technologies such as ZigBee/6LoWPAN or IEEE802.11ah are only suitable for short-distance IoT coverage and cannot guarantee reliable network coordination control. The cost of satellite communications is prohibitive, energy-intensive, and unable to reach indoors.
The times are calling, the cellular network is coming over
The Internet of Things is a shock, hooked up to the global 2/3/4G network, and with him at least ten years of struggle.
The 2/3/4G network is like a rich generation, mature and stable, gentle and golden, and also has a special sense of security. It has a wide network coverage, dense distribution, and reliable network coordination control, which not only ensures the security and effectiveness of the Internet of Things, but also is easy to plan, manage and monitor. The Internet of Things can be directly connected to the off-the-shelf base station, and you can stay in a villa dream.
In order to cope with the fascination of the Internet of Things, the 2/3/4G network began to repair both inside and outside, reviving the glory. It enhances coverage, reduces power consumption, reduces device complexity, reduces latency, and minimizes cost per bit.
After all, after a few generations, there is also a time when the power is not enough.
GSM capacity is limited and cannot meet the simultaneous access of a large number of devices. The rich generation is very hard, it reduces signaling overhead, controls overload, tightens resource granularity, and expands coverage. However, this is only a matter of expediency, such as supplementing male hormones, not the fundamental road to the future, and the days are still long. . The power consumption and access delay of GSM made the Internet of Things realize the regret of the first night.
As for 3G (UMTS), the working frequency band is higher, the coverage is small, and the indoor coverage is poor. At the same time, the UMTS module is much more expensive than the GSM module. Pass!
The nightmare is easy to forget, and the initial heart is hard to change.
LTE was designed for data flooding and did not consider IoT requirements at first.
Telling the truth, every time I hear that LTE wants to bear the Internet of Things, I feel that it is dead.
The characteristics of the LTE network are: few devices and large traffic. A small amount of equipment is almost negligible compared to massive data traffic.
The characteristics of the Internet of Things are: many devices and small traffic. Massive devices are out of sporadic packets, and signaling traffic is exploding, causing network failures to be impossible.
LTE with the Internet of Things faces many real-world challenges, including control overhead, energy efficiency, coverage enhancement, robustness, security, and scalability.
The most worrying thing is that the Internet of Things business and traditional voice and data services coexist. How to avoid the impact on traditional services when large-scale IoT devices are connected?
The LTE random access procedure (RACH) is first placed on the countertop.
When the UE (mobile phone) is to establish a data connection with the base station (eNodeB), in order to establish synchronization with the network, the random access procedure is triggered by the UE. RACH consists of a series of time-frequency resources called RA slots. The UE sends an access request to the eNodeB using the preamble sequence in the RA slot.
There are two types of LTE random access procedures: non-competitive random access and contention random access. Each LTE cell has 64 preamble sequences for non-contention and contention random access, respectively.
The non-competitive random access is controlled by the network, which can avoid collisions, reduce the access delay, and guarantee the access success rate, for example, in the handover scenario. This does not affect the IoT business.
Affecting the Internet of Things business is a contention-based random access process.
(1) Preamble sequence transmission (Message1)
(2) Random access response (Message2)
(3) Message3 transmission (RRCConnecTIonRequest)
(4) Conflict resolution message (Message4) In the contention-based random access process, two collisions occur.
First conflict:Message1: The UE randomly sends a preamble sequence to request access. Since the preamble sequences are orthogonal, the same RA slot allows multiple UEs to use different preamble sequences. In this case, the eNodeB can decode the request.
If two or more UEs use the same preamble sequence, a collision occurs, causing the eNodeB to be unable to detect the request.
Of course, even if multiple UEs use the same preamble sequence, the eNodeB may be able to detect the request because the received signal strength is different. However, this causes the eNodeB to send the same Message2 (random access response) to multiple UEs, which will trigger a second collision at Message3.
Second conflict:If different UEs receive the same Message2, they will get the same uplink resource and send Message3 at the same time. At this time, the second collision occurs.
The random access process becomes the first challenge for the LTE bear to embrace the Internet of Things, because signaling occurs when a large number of IoT devices attempt to access the base station at the same time (for example, when an earthquake occurs, all seismic monitors in a certain area simultaneously issue an alarm) The spikes cause PRACH overload, the possibility of access competition increases, and the access delay and access failure rate increase.
Although, in order to reduce the PRACH load, we can increase the access schedule in each frame, however, this will reduce the data transmission resources, resulting in tight uplink channel data transmission capacity.
Also, the allocated RA slots in the LTE frame are limited. At the same time, the Zadoff-Chu sequence processing adopted by the PRACH preamble sequence is limited by the computing power of the IoT device.
In short, LTE is difficult to cope with large-scale IoT device access, and the access delay and access failure problems caused by it will affect traditional data (and voice) services. Of course, this will also affect the IoT service.
Fish and bear's paw can't have both.
There are also solutions.
For example, the separation of access requests between people and things mainly includes three types: forced separation mechanism, soft separation mechanism and hybrid separation mechanism. Forced separation perfectly isolates access requests between people and things. Soft separation refers to the sharing of resource pools between people and things, but with different access possibilities. Mixed separation is a mixture of the first two.
For example, the FastAdapTIveSlottedAloha technology uses continuous idle or collision time slots to estimate the number of IoT devices activated in the network (network status) and quickly update the transmission possibilities of IoT devices, thereby reducing access latency.
For example, the clustering mechanism randomly distributes the Internet of Things devices in a certain cell, and divides the Internet of Things devices into multiple clusters, and each of the clusters selects a coordination (Coordinator), which is the only device in the cluster that directly communicates with the base station. And as a relay node that communicates with the base station by other devices in the cluster. This not only limits the number of devices that access the base station at the same time, but also reduces the power consumption of the entire system.
However, all the methods are “for research and testing onlyâ€, and LTE and the Internet of Things are going to be commercialized, and there is still a lot of work to be done. At the same time, the IoT application scenario is all-encompassing. It requires more flexibility for the network. How to design and optimize it, how to not affect the traditional business of the operator (after all, there is a higher ARPU), all on the road. problem.
So, does 5G hold the Internet of Things?Massive MIMO, heterogeneous networks, millimeter waves (mmWave), SDN/NFV, are generally considered to be several key technologies for 5G. Can these key technologies adapt to IoT needs?
MassiveMIMOMassiveMIMO uses spatial diversity to improve spectrum efficiency by deploying antenna arrays with more cell terminals on the base station side. This feature enables base stations to simultaneously accept multiplex transmissions, which seems to be very suitable for large-scale IoT device access. The question is, how many antennas do you need to deploy on the base station side for large-scale IoT device access? Can technical breakthroughs be made?
Heterogeneous NetworkWe say that the future network is a heterogeneous network, and many smallcells are deployed in the network to solve network capacity requirements.
However, this is to solve the capacity and increase the speed of the network. For the Internet of Things, the key is not network speed, but coverage, which is a reliable and ubiquitous connection, which runs counter to the problem of smallcells addressing hotspot capacity.
The demand scene for people and things is completely different. For example, a rural highway is a key coverage area for the Internet of Things, but it is not a data-intensive area. There is no consistency in coverage between people and things, which is not economical for operators to invest. Even in the dense areas of IoT devices, the ARPU value brought by IoT services is far lower than that of traditional services. If investment returns are considered, operators are not willing to deploy smallcells for the Internet of Things.
Millimeter wave (mmWave)Millimeter waves show irresistible charm to 5G with its wide spectrum resources. The millimeter wave is characterized by fast speed, short coverage distance and high power consumption. These three characteristics are completely opposite to the requirements of the Internet of Things. The characteristics of the Internet of Things are: low speed and coverage distance.
Millimeter waves show irresistible charm to 5G with its wide spectrum resources. The millimeter wave is characterized by fast speed, short coverage distance and high power consumption. These three characteristics are exactly the opposite of the IoT requirements. The Internet of Things is characterized by low speed, long coverage, and low power consumption.
SDN/NFVSoftware Defined Network (SDN) and Network Function Virtualization (NFV) make the physical network more abstract, which facilitates flexible management of network resources and supports different types of services. SDN/NFV provides different data streams according to different services, and can be dynamic. Scheduling network element functions that have been virtualized, which is excellent for the Internet of Things.
On the one hand, SDN can separate the human-to-material service, and at the same time guarantee the QoS of the separated logical network, effectively utilize the network resources, and alleviate the network problems brought by the large-scale IoT device access.
On the other hand, NFV can dynamically manage the network structure according to traffic demand. For example, NFV can “deform†the network element of a certain area at any time according to the traffic demand. It can be an IoT data collection center, or it can be used to extend the coverage of the relay, or change back to the base station to deal with the temporary. The peak of the access request.
In fact, SDN/NFV allows us to see the potential of future "unlimited capacity" networks.
However, SDN/NFV will bring about disruptive changes in the network structure, and even subvert the entire industry chain. Equipment vendors to promote virtualization is like breaking their arms and fighting each other. Even if the operator is determined, how big is it is unknown.
Shenzhen Yidashun Technology Co., Ltd. , https://www.ydsadapter.com