Analysis of field data from several large LTE network deployments found that a MME can experience a sustained signaling load of over messages per user equipment UE during the normal peak busy hours and up to messages per user per hour under adverse conditions. The rise in core signaling can also be attributed to an overall increase in network usage by LTE subscribers.
In some large US metropolitan markets where LTE is available, network peak usage is as high as 45 service requests per UE per hour in peak busy hours. As LTE grows in popularity, signaling in the EPC will continue to rise, which increases the potential for control plane congestion and signaling storms if not properly managed.
As a result, Mobile Network Operators MNOs must take steps when moving to LTE to ensure that their core control plane network can support the expected increase in signaling volume.
Paging is required to locate a UE in the network when it is in an Idle state, making its exact location in the network unknown. Paging procedures are used by the network to:.
In addition to high generating signaling volumes, both paging and TAU procedures are a significant power drain the UE battery. It is therefore important to carefully design TAs so they are neither too large to minimize the volume of paging, nor too small to prevent frequent TAUs and avoiding toggling at TA borders.
This helps MNOs lower the volume of paging while still meeting end-user quality of experience expectations for each type of service. The WMM paging policy supports the following configurable parameters:. Table 1 shows the UE power and battery life savings for a smartphone using dynamic TA management features as compared to a smartphone using basic TA list management capabilities. The comparison is for an LTE smartphone with a power consumption profile of:.
With LTE and its all-IP architecture, a new set of analytical tools is necessary to maintain the network. Using traditional Radio Access Network RAN management tools is time consuming, resource intensive and has a number of limitations:.
In addition, because the end-user mobile devices are used to collect the data, the need for drive testers is significantly reduced.
As smartphones and tablets with always-on applications and services proliferate and the competitive push to move to LTE increases, MSPs must consider how they will address signaling challenges.
The Recent 4G LTE Network Vulnerabilities and Attacks
MSPs can resolve customer issues faster and improve network performance to increase customer satisfaction and reduce churn. Those who make it a priority to address the signaling challenges that come with this move will be in a better position to achieve a timely return on their investment. To contact the author or request additional information, please send an email to networks.
Dave is a senior product marketing manager at Nokia with over 25 years of telecom industry experience. In his spare time Dave plays sports, runs the odd marathon and enjoys good craft beer - not necessarily in that order. Blog Home. Paging procedures are used by the network to: Request establishment of a non-access stratum NAS signaling connection between the MME and the UE to support a network service request. Prompt the UE to reattach itself to the network after a network failure.
The comparison is for an LTE smartphone with a power consumption profile of: mW for transmit mW for receive 5. Using traditional Radio Access Network RAN management tools is time consuming, resource intensive and has a number of limitations: Drive testing provides only a sample of the network coverage at ground level. It is also time constrained and reactive. Service measurements aggregate data across all users. This aggregation is useful for detecting hardware faults but not for detecting individual customer performance issues.
Using call tracing to solve specific customer complaints can require the subscriber to make test calls while troubleshooting takes place. This is not always practical. It is also time consuming and may still result in the need for a costly field visit to replicate the user behavior. Improved network analytics bring benefits across the MSP organization: Customer care: Personnel can quickly identify coverage and device issues to provide rapid responses that can improve customer satisfaction and lower call hold times.
Operations: Personnel have the data analysis and reports needed for continuous improvement and quality management. For example, with data from end-user devices, coverage holes, dropped calls and cell performance issues can be identified and key performance indicator KPI targets for improvement can be set. Engineering and network planning: Personnel can use traffic pattern analysis with accurate radio frequency RF measurements to predict and verify coverage requirements.
This information also assists in RF coverage and capacity planning and utilization, helping to lower capital costs with more targeted RAN investments.In this section, I will go through a typical protocol sequence of LTE packet call. This will be the backbone structure for all other call processing. Followings are the topics to be explained in this page. Understanding a complete a call processing steps means understanding everything about the technology.
So putting all the details of the call processing in this one page is impossible. Following is the over protocal sequence being exchanged between UE and Network. Actually understanding all the details of these steps would be the goal of your whole LTE career. Basic State Machine. Following diagram shows a possible state machine that a UE would go through. Most of other transition will be described in "Handover" page.
Of course, there would be a small variations but overall concept would be almost same. Following would be two major variations. The example test sequence in this case shows the second case.Minimum n Maximum Paging Periodicity in LTE ?
Big Picture First. But I think there are a couple of big pictures that may help almost anybody working in full protocol stack.
First big picture I would like to introduce is the channel mapping as shown below. Just try to pick any RRC messages and try to follow the arrow for the message. Following is a sequence diagram showing not only the message but also basic configurations of each layer.
More detailed description of each layer in the context of full protocol stack will be explained in " Full Stack " section. Just read through this sequence whenever you have time until you can duplicate the sequence without looking into this again.
This can be a good framework for your study and good guide for troubleshooting. RACH Response. RRC Connection Request. RRC Connection Setup. RRC : dlInformationTransfer. EMM : Authentication Request. RRC : ulInformationTransfer.
EMM : Authentication Response. EMM : Attach Accept. RRC : ulDirectTransfer. EMM : Attach Complete. The diagram you saw above a kind of message flow event diagram in time sequence. The diagram shown below is not a time based, but it shows the channel mapping or data flow across the full protocol stack. Pick one of the message from the diagram shown above and try to find right route for this digram and see how much details you can add.There are a number of myths about paging.
LTE KPI Optimization Deep Dive: RRC Success Rate
Paging is not only used to bring a UE from Idle to connected mode. It is also used in RRC Connected mode. It is used for the following use cases. From the picture above. There are two types of paging with respect to which node will initiate paging i. The range for paging cycle varies as 32, 64, and up to radio frames. The range of allowed values is the same as those used in SIB 2. Well, for paging to take place. Operators set up paging cycle.
Paging cycle is measured in Radio frames. Commonly used value for Paging cycles is Therefore, if an operator has setup default paging cycle as It means UE will wake up after every 1.
After waking up. If it does not find paging information related to the UE it will go back to sleep. Within the radio frame, there are 10 subframes. UE does not remain awake in all 10 subframes. Instead, it wakes up in a specific subframe either subframe 0, 4, 5 or 9 within a radio frame. In order to find out which paging frame the UE will wake up in. Once UE has computed the paging frame. It goes ahead and finds out in which subframe of the paging frame it will wake up.
A UE does not need to wake up in all one 1 msec subframes within its Paging Frame. UE makes a use of the look-up table. The value of Ns is cell-specific so cells carrying low quantities of traffic can be configured with a value of one 1 to provide relatively low paging capacity, while cells carrying higher quantities of traffic can be configured with a value of 4 to provide relatively high paging capacity.
Subframes 5 and 0 were not selected for the lower capacity configurations likely to have smaller channel bandwidth because subframe 0 already includes Masters Information Block MIB and subframe 5 already includes System Information Block 1 SIB 1.
The high capacity configuration also uses subframes one 1 and 6.Paging is the mechanism in which Network tells UE saying "I have something for you". In most cases, this paging process happens while UE is in idle mode. This means that UE has to monitor whether the networking is sending any paging message to it and it has to spend some energy battery to run this "Monitoring" process. If I have to run this "Monitoring" process continously even in the idle mode, isn't it too much waste of engergy?
Yes, it is. Is there any way to prevent this kind of energy waste? There would be no way to prevent this envergy consumption completely if you can come out with any idea to prevent this completely, you don't need to read this any more. What is it? There may be many different way to do this. What kind of contract it would be like? It is like "Hey. I will go sleep when you are not transmitting Paging and I will just wake up exactly at the time you are transmitting the paging message".
This way UE can save the battery while it is in sleep and can get the paging message as well. It means that UE is recieving some data from the network "discontinously". Here we have an important question. How can UE knows the exact timing when the Network send the paging? The simplest solution for this would be to make another contract about "Paging transmission timing".
Overview on Paging Mechanism. Note : Each eNodeB can contain cells belonging to different tracking areas but each cell can only belong to one Tracking Area. Paging Parameters in SIB2. Now it's time to get into the official specification. Paging Occasion and Paging Frame. As you know, LTE has two timing units as many of other technology.
Let's tackle the PF first. Then where does T come from? According to Then which value does UE has to use? It depends on the situation. If upper layer send the value, it use the value from the uppder layer, otherwise UE has to use the value from SIB2. Then let's think about where does other values come from. These values are defined as follows in the specification. Refer to By this, we got PF now.Since I got a lot of requests to explain the LTE paging mechanism and paging capacity, so I decided to write a couple of short articles on these topics.
Paging is a mechanism to initiate services for UEs that are in idle mode. Idle mode transition is important to conserve battery of the UEs. However, a procedure has to be defined to access the users in idle mode if there is downlink data for them.
LTE Paging Explained
This process is the paging mechanism. The main parameters that determine the paging capacity at the eNB are given below:. Usually it is set to ms or frames. This means that if a UE woke up in frame 3 then it will wake up again in frame after frames and then at frame and so on.
However, this only indicates that there is a paging message in this subframe but it might not be addressed to that UE as there can be multiple UEs using the same paging cycle. If NB is set equal to T, then every frame contains one Paging subframe. If NB is set to 2T, then every frame will contain 2 paging subframes. So, in short, this parameter can impact the paging capacity but at the same time it can increase or decrease the paging overhead as well.
This is also shared in SIB The UE then sends the RRC Connection Request and the cause value of this request is set to mt-access which indicate that the UE is initiating the connection due to a paging message. However, this timer only works for PS pages and not for CS pages. In case of CS page, the page is retransmitted from the CS core. Impact of Default Paging Cycle : The paging cycle or T as explained above tells the periodicity with which the UE wakes up to check the paging messages.
The smaller the value of T, the UE will need to wake up more frequently. This means that a smaller value of T will lead to higher battery consumption or utilization and UEs will have to be charged more frequently.
However, a larger value means that the latency for the UE will increase. For instance, if we use ms for T, the incoming pages at the eNB will be buffered longer on average and that will increase delay. So, a compromise needs to be maintained between battery consumption and expected paging delay. Paging Failures : Another important aspect is to ensure that paging messages are successfully reaching the destined users. The paging failures can be caused by decoding issues if the paging modulation scheme is aggressive or if the PDCCH allocation for paging is not using a robust aggregation layer.
When the UE moves from one tracking area to another tracking area, it initiates a TAU and if during this process a paging message is received then the UE might not be able to read it as it is undergoing a TAU. Thus, it is very important that the TAC planning is properly done to mitigate this issue. I will address the TAC dimensioning and paging capacity in the next short article. In case of any queries or feedback, please drop a comment below and I would love to respond and help.
Thank you for this topic.So why do we need to wake up the UE? Again there can be multiple reasons for it such as downlink data, change of system information or even earth quake or Tsunami warning or fall back to lower access technologies like CDMA in all these case the UE needs to be woken up in case it has entered a RRC IDLE state.
Now, how does the UE know when to look for Paging messages? If there is any Paging for it then it will react to it by triggering a RRC connection request message. How is Paging transmitted on LTE physical layer? Of course it goes on PCH, physical Paging channel. Well, not much, the encoding process is very similar except for few restrictions that apply for only PCH. He transport block that comes to physical layer for PCH is not usually a very huge one, but there can be multiple UEs Paging message multiplexed in the same transport block though.
The transport block size for the PCH is restricted to the maximum possible transport block size that is possible for QPSK for maximum possible resource blocks in the given system bandwidth. This is some basic information about Paging.
When paging has to be sent to UEs to indicate that there is some change in the system information, is the paging message sent to each individual UE? I mean to say, that since the change is at the system level is there any common paging message which is read by all the UEs. Is paging message dedicated for a single UE? It will be a great help. Thank you. Basically all UEs which are in RRC Idle mode has to wake up during the paging cycle and decode the paging message to see if there is any UE-specific message within the decoded paging transport block.
If yes then respond to it with a RACH else go back to sleep. Everybody mention that ue wakes up and ue goes to sleep mode,here UE means which entity?? The paging transport block can have message to one or many UEs which are idle. So the UE has to decode the paging message and check the same. My qn is ue means which entity comands it to check nd sleep. If there is no paging, it goes back to sleep and will wake up after 1. We dont see the paging message in the UElogs.
Does the UE monitors the paging channel every 1. What is the purpose of paging? Is it only to trigger the UE to be establish the RRC connection to receive any incoming data or to notify the UE of an incoming call as well. Please let me know your thoughts on this.CS Fallback. Basically LTE is a Packet only technology. It is well designed for data traffic.
Then what about Voice call? There can be a couple of options to achieve voice call in LTE. One of the option is just to use packet based voice call e. Another option is to use multiple technology. This technology that enables to redirect connection to other technology e. It may sound very simple and usefull First, UE should support multiple technologies and network side would be even more complicated. One of the simplest representation on network side would be as follows.
Now let's look into the interplay of the two networks to make the voice call possible. I think these interplay can be explained by adding just three lines as follows. Is this everything make CS Fallback happen?
Definately not. To make these two different protocol work together would not be that simple. It is not the scope of this short section to describe the whole details of 'CS Fallback' protocol side. So just keep it mind that it would be pretty complicated process and try to google some of articles. These are not the full list of those situations, but can be most common situations triggers for CSCF.
User make voice call MO Call. For the details of 'Redirection' mechanism, refer to 'Redirection' section.