Locating a mobile subscriber using spare DCC (1997-08-23)

1. Abstract

In the market, a mobile unit can send and receive a short message via a mobile telephony network or satellites, but we will discuss the short message service (SMS) handling between a Message Center (MC) and a mobile unit. Furthermore, we will describe how to locate the exact position of a mobile unit by using a digital control channel (DCC).

2. Marketing Analysis

This system could be used by

·        Police department

·        Adventurer

·        Blind persons

·        Any organization

·        Tourists

·        Adventurous games’ organizers

3. System Analysis

3.1 Determine location of a mobile unit via satellites

·        There is a system available in the market that assists blind persons to find out his position and suggest a path taken to destination. That system combines with an electronic geographical maps and costs about thousands of Canadian dollars. The satellites returns longitude and latitude of user, and system computes the exact location of the user.

·        The system, which includes a laptop and a special alphanumeric keyboard, allows user requesting his exact location. This may require annual subscription to satellite services plus access to an electronic geographical map. Thus, it is an expensive product.

3.2 Determine location of a mobile unit via a mobile telephony network supporting DCC.

·        A mobile unit must register whenever it enters a new cell site or location area. Its position (cell identity) should be reported to the serving Radio Base Station (RBS), this cell identity will be relayed to the serving MSC. Thus, we can determine which cell the mobile unit is in by printing out its cell identity (applicable for both analog and digital control channel), which could be stored in the serving MSC, HLR, or an MC.

·         Remember that a mobile unit is able to register on either an analog or DCC. However, it only receives SMS that is sent from an MC or MXE over the DCC. Therefore, we will consider using DCC of the serving cell and adjacent cells to compute mobile unit’s exact location.

3.3 Short Message Services

·        This feature allows users sending an SMS from a MC to a mobile unit or a cellular phone. In the market, this feature supports mobile unit that is capable of handling messages over DCC. However, when a cellular phone is busy (on voice channel), the MS doesn’t deliver that message. The HLR will inform the MC to delay that message delivery.

·        Options: If the MSC buffered that short message, we would consider cases that the mobile unit “hands off” to another RBS belonging to another MSC, i.e. the anchor exchange no longer has controlled over the mobile unit. Thus, it may be better to get the MC resending the short message. Note that: the HLR will inform the MC when the mobile unit is free.

4. Implementation overview

·        Using the spare DCC (TDMA), we may be able to communicate with the mobile unit roaming in cellular telephony network, and report its exact location toward an HLR, an MC, or serving MSC.

Figure 1. Locating distance of a mobile unit in a location using RBS.

·        As shown in the above diagram, a mobile unit is roaming across the border of 3 cells, which 2 of them belonging to MSC-2, and 1 cell is served by MSC-1.  Thus the mobile unit has been capable of tuning to all 3 DCCs, collecting their cell identities, original transmitting power, and receiving signal strength of each cell. Based on those data, the mobile unit should be able to compute its distance from 3 RBS. It then relays the findings to the RBS that has highest signal strength. That serving MSC will send a report to the HLR or an MC. These operations are carried out on a spare DCC of each cell (each cell site is served by an RBS). This way we could avoid using the principal DCC, which is dedicated for paging mobile station (MS), delivering SMS, etc.

·        An exact location of the MS in terms of building, streets or address will require an electronic geographical map.

Figure 2. Hardware modification of a mobile unit

5. Future enhancement

·        An adaptor connected the mobile unit, e.g. MS, to a laptop computer could be serve as mobidem that allows users connect their laptop to an Internet service over the air.

·        Nokia planned to design a portable unit that looks like a mini laptop when it opens. It functions as a mobile phone if closes.

6. References

·        Mobile Communications Design Fundamentals, Williams C. Y. Lee, Section 6.5.1 on “Conversion between dBu and dBm in power delivery. See also section 9.2.1

7. Update Notes (2018-12-11): back to 1997, I didn’t know that building and construction between an RBS (radio base station) and a mobile phone would change the signal strength measurement that makes computing distance inaccurate.

Wireless earphone and cordless phone (1997-08-20)

1. General Information

The wireless earphone combined with antenna connected to a sound system would increase mobility and privacy to users. We would discuss other applications using similar method in the following sections

2. Marketing Analysis

This system would be sold to all users using a sound system such as

·        Music listeners, TV users

·        Technical support personnel

·        Car alarm system

·        Cordless phone or ear phone

3. Product Analysis

3.1 System Overview

There are wireless earphones and cordless phones in the market that have interference problems, e.g. a user uses a wireless earphone listen to music might hear unwanted sound/message/music coming from a neighbouring wireless sound system. To eliminate this problem, we may want to encrypt voice data before sending it on the air from a sound system to the wireless earphones.

3.2 Voice Encryption

If we planned to use voice encryption method and CAVE algorithm designed for cellular telephony, cost of each earphone would be very high. The processing power of each earphone is also slow. Therefore, it is recommended to use in cordless phone handset.

Assuming that user is only listening to music from his sound system, but he is not concerned with eavesdropping. Thus, the earphones will only focus on decoding voice data sent from his sound system, but ignoring data sending over the air by other sound system. The same principle applies to his sound system.

3.3 Implementation Proposal

Encoding/digitizing voice data and adding some pre-defined (product) identification code at the beginning of each voice message frame. This unique code must be stored in both sound system (cordless phone, music receiver, etc.) relayed via the antenna as well as the earphone. Therefore, the antenna and earphones will only accept and decode messages which convey the same predefined identification code.

A manufacturer would set the product identification code in both devices. It may contain

·        Serial number

·        Manufacture code allocated to each manufacturer

·        Model number

The diagram above illustrates how system would add and remove identification code. It must be implemented on both sound system and ear phones.

(a) When interference detected either the earphone or radio-based antenna system will order changing frequency of transmitted carrying waves.

(b) The receiving unit will perform verification on identification code, parity bits, frame alignment bits, etc. to ensure quality of the receiving messages.

4. Other applications

The above procedure could be implemented in car alarm system using remote key.

Toll free and dial up services (1997-08-18)

1. General Information

Most business offers 1-800 toll free service to their customers, thus they are able to enquire information about new product, to perform transactions on telephone without paying long distance charges.

For example, an assurance company in North America would issue only one toll free number, e.g. 1 (800) 345-6789 and has some offices in major cities as Montreal, Toronto, New York, and San Diego. When a customer living in New Brunswick dials the above toll free number, the center which receives call will analyze the area code + NPA of the customer phone and dispatch the call to the nearest service branch, e.g. call is routed to the branch in Montreal.

The above feature could also be deployed to offer Personal Communication Services to telephone/computer users who travel frequently and require access to their home computer system from the hotel. The main/home office would authenticate his request, analyze his calling number, and allow him to log on to a local office, where he is. (The authentication and login process will be done in the background or transparent to the user. The main office is responsible for updating the local office all information that his user needs. After his user hangs up, all transferred personal data should be purged in the local system for security.)

2. Marketing Analysis

As discussed in the previous section, the telephone system operator can setup their system so that all calls will be handled automatically without operator’s assistance. Therefore, there is no need to have a person sitting in the main office and dispatch incoming calls to an appropriate branch. Some companies would be interested in this feature:

·        Food or furniture delivery

·        Company that offers on-line services

·        Car/home Assurance Company

·        Technical Support Center

·        Banks, Master card, Visa, American Express, or credit lines’ organization.

·        Police department

·        Any organization

3. Feature Analysis

3.1 Toll Free Number

·        In the cellular or mobile telephony network, this feature could be easily implemented in the Service Control Point (SCP). As system access, a mobile unit would send his phone number (MIN), and dialled number to the serving MSC. These numbers will be forwarded to the SCP, where those numbers would be analyzed properly based on the toll free number (B-number), and the area code + NPA of caller. SCP will return the new B-number (nearest local service center) and caller’s number to the serving MSC, where a call setup will be performed based on new number (B-number). For example, the SCP operator could create a look up table with Area code and NPA as the search key.

·        A landline telephone network operator could also build a similar system to offer this service to their customers.

3.2 Dial up Services

·        This service helps travelers to retrieve all necessary information and services as he sets up at home office on a short or long term business trip. This helps users to speed up quickly in a new environment.

·        To transfer data and information from his home office to a visited company, an authentication between his home and host company are recommended. More details will be discussed in the next section.

3.3 Process of data transferred between home company and host company

When the traveler is on a short trip, he will dial to his home company as usual, the home company shall perform the following analysis before connecting his employee to the host company (usually a subsidiary company):

·        Authenticate his employee for password and authorization of having need of an account and his business trip duration.

·        Home system will request the host company of setting up a temporary computer account for his employee

·        If authentication process went fine, the host company would setup an account and receive all information and data from the home company.

·        The home company would send his employee the host company dial-up phone number before disconnecting the current call.

·        The employee’s computer (laptop) would use the new phone number to connect to the local host’s computer network.

These notes were written or draft back in 1997. At that time, only dial-up services were offered by Internet Service Providers. Currently, user could carry his laptop to the subsidiary offices, all papers had been communicated between his home office and visited office, i.e. clear to get a WiFi password to remote access to his home office by a secured communications such as VPN. He could download documents or tools down to his laptop by using VPN. Downloading his home/personal settings and data to network of a subsidiary branch would expose security risks.

Cellular Network Traffic Simulator (CNTS)

1. General Information

In this document, we will present a model of a Cellular Network Traffic Simulator (CNTS) that would be used to generate traffic in network to test mobile telephony features.

2. Marketing Analysis

This system could be used by

·        Cellular network operator

·        Telecom system provider

3. Product Analysis

3.1 Cellular Network Traffic Simulator

Figure 1. Network diagram of CTNS with other components

3.2 Implementation Proposal

CTNS could be connected to an MSC, HLR, or other nodes under network tests via a Message Routing Center. CTNS could provide the following

·        Emulating an MSC, a HLR, or a Service Provision Node, e.g. voice mail machine, and authentication center, or a message center.

·        Generating traffic load to other “real” nodes such as MSC, HLR, etc.

·        Allowing tests of new features in an emulated environment.

3.3 Graphical user interface

CTNS will provide a friendly user interface that allows users specifying or developing signals, messages with data in windows.

3.4 Message Routing Center

This is a special node or router to route message from the CNTS toward an MSC or HLR under tests. This is to save work in implementation of numbering plan on all components in network.

4. Ericsson’s existing products

Ericsson has developed a product called CTSIM to simulate phone calls from a mobile phone. CTSIM could also provide many calls from different mobile phone numbers that used in traffic mix tests.

Ericsson also has emulated APZ (not APY) to load mobile phone software in order to perform simulated function test by developers before real equipment tests.

In this case we could use emulated APY as CNTS and connecting CTSIM to a real MSC to generate some mobile call traffic.

The CTNS would generate heavy traffic toward real HLR and MSC while network testers performed their test cases. The CNTS could be another MSC in this case.

If users wanted they could develop a platform to load Message Center (MC) sending many SMS toward CTSIM or mobile users on a real MSC. Ericsson has a product called UBSIM, which sends SS7 messages to HLR to test HLR’s functionality. UBSIM could be modified or provided a suite of SS7 messages to generate traffic loads on real MSC and HLR as a MC.

To emulate voice machine such as Octel, we probably have to use emulated CNTS (APY) to generate heavy voice calls, i.e. seizing voice trunks, because there was no ISUP emulator as I knew of.

To make testers life easier, developers should provide a suite of messages in good format. Testers only need to load those templates and modify the messages for each test case. They could create a program or a loop to send numerous messages to a node under test.

It is assumed that usual function tests and system integration test had been done. The main goal of this network test is to create high load and many combination of call traffic in system in parallel. Hopefully a weird combination of calls would come up to fail the system. Each test scenario in this activity would expect successful or failure calls. Thus network tester would load after-test result database including log files on a super computer to crunch data to ensure that successful calls were completed as expected AND some key failure cases failed AND checking a few spots in database to ensure data were not corrupted. There would be many call cases to crunch, thus we must narrow down to check key scenarios.

Dynamic Time Allocation Model (1997-08-21)

1. General Information

Time supervision is a key element in management, and in supervising task of real-time software.

2. Marketing Analysis

·        In the next section, we will discuss a Dynamic Time Allocation Model (DTAM) that can be used in development of real-time software to maximize its working capacity.

·        Mutual Fund company, e.g. in RRSP the limit amount of money invested in foreign content is 20%.

·        The maximum capital loss of a security or stock, i.e. stop loss based on a threshold or market trend.

3. Product Analysis

We will take an example of development of a mobile telephone software system to illustrate the use of DTAM.

 T_totalmax = t_1max + t_2max + t_3max

 T_Total = t₁ + t₂ + t₃ + … + t_n

·        DTAM Unit allots time required to execute each sub-process and maximum time needed to complete a call set up. It can extend time to execute a sub-process as long as the total limited time does not exceed T_totalmax. See the following example for details.

·        For instance, a call set up via Signaling System #7 (SS7) requires the gateway to fetch the dynamic roaming number (RRNB), which is used for routing call from the gateway to the visited MSC. The gateway is then used the RRNB to set up the voice path for both calling and called party via voice trunk. Assume that it takes t₁ for registration, and the VMSC could not page and put the MS on voice channel after t_2max due to congestion. The DTAM Unit calculates required time and allows GMSC sending another paging request attempt to the VMSC as long as: T_total <= t1 + t_2max + t_3min + … + t_nmin. This helps to survive a call delivery to our customer.

·        Therefore, DTAM unit controls and allots execution time for all sub-processes.

If we could allot maximum time in a VMSC for paging a mobile phone, we could save processing from sending back “congestion” message to the GMSC, and then getting a paging request again from the same GMSC. If the entire process to set up a call is a few seconds, which would be spread among GMSC and VMSC for processing a call including authentication, locating subscriber, paging subscriber, reserve an air voice channel, and set up voice channel in the voice trunk. The process sending message back to GMSC in case of congestion and another paging request came from GMSC may take half a second in the process, therefore VMSC could buffer that paging request for ½ second before attempting second paging request. Why waiting ½ second? This is to wait a subscriber released his voice channel during this period.

4. Administration Procedure

The system administrator is responsible for defining the following data:

t₁, t₂, …, t_nmin: minimum time to execute sub-process #1, …, #n.

T_total: total time permitted for a process

5. Stop loss based on market trend of new value of a stock performance

Using hard stop loss is not a good strategy, because you may hold shares to rebound after a short period of panic selling.

Let consider this case, your share was $100 and your stop loss is $80, i.e. 20% of your current share price.

·        System records both current share price, stop loss and percentage loss for selling share

·        If your share price has gone up to $200, the stop loss would be adjusted to $160, i.e. new peak price.

Market trend indicator could advise your system something on the common stock indices such as NASDAQ, NYSE, etc.

·        If the market trend is going down since the stock reached $200 to $160. This could be a panic selling (bear market, disaster, or short-term worldwide issues); it’s not about performance of this company.

o   System could alert you by email or text messages to validate news about the company at 10% loss based on new peak

o   If you didn’t adjust the stop loss, system would trigger a sell at $160, if share slides down to this price.

·        If the market trend is fluctuates normally, i.e. a little bit of up and down, this is really a case to read news and analyze the issues or sell shares.

6. Reallocating your foreign investment automatically

6.1 Maximum foreign content

Since the maximum content of your foreign investment is 20%, you could set system to transfer funds around to meet this requirement by government.

You could preset the target fund if foreign investment is overflow, so system would transfer money from that foreign fund to it.

6.2 Rebalancing your portfolio

Some strategist suggests to maintain or to balance out our investment between growth fund and income fund based on our age.

You could set this percentage of fund allocation in your system, so it could be transferred automatically for you.