The invention relates to a method, a network, a network element, a micro or pico cell base station, a terminal and a software product for providing allocation of frequencies in a mobile communication network.
Multi-carrier technology is very likely to form a basis for future radio technologies in so called 3.5th and 4th generation radio networks. One example of a multi-carrier system is the OFDM (Orthogonal Frequency Division Multiplexing) system, wherein data is transmitted by dividing it into several interleaved bit streams that are used to modulate several carriers.
Multi-carrier systems, however, pose problems for frequency planning due to the fact that terminals using several frequencies or frequency bands cause both intra-cell and inter-cell interference. Therefore, an effective solution for dynamic frequency-planning in a mobile network and use of such a network is called for.
An object of the invention is to provide a method, a radio network, a radio network element, a micro or pico cell base station and a mobile terminal to alleviate the aforementioned problem and provide an efficient manner to use frequencies in a radio network.
In one aspect of the invention, there is provided a method of allocating frequencies on the uplink of a radio network, the method including allocating a same set of uplink frequencies to be used in two adjacent coverage areas of the network, wherein the set of uplink frequencies is allocated according to a different allocating priority in the two adjacent coverage areas.
In another aspect of the invention, there is provided a radio network, wherein the network is configured to use a same set of uplink radio frequencies in two adjacent coverage areas of the network, and wherein the network is configured to allocate the uplink frequencies in the adjacent coverage areas according to a different allocation priority.
In still another aspect of the invention, there is provided a radio network element, comprising means for communicating, in a first coverage area, with a mobile terminal applying a primary frequency, means for communicating, in the first coverage area, with the mobile terminal by applying one or more secondary frequencies, if the mobile terminal can support and requests for one or more secondary uplink frequencies, wherein the radio network element is configured to allocate the primary frequency and one or more secondary frequencies from a set of frequencies, the set of frequencies being the same set of frequencies available for allocation in a second coverage area next to the first coverage area, wherein an allocation priority of the frequencies in the set of frequencies is different in the first coverage area compared to an allocation priority of frequencies in the second coverage area.
In still another aspect of the invention, there is provided a micro or pico cell base station, comprising means for providing a radio cell, wherein the radio cell is in an operation area of a macro cell, the micro or pico cell base station being configured to use a same set of frequencies as a macro cell network, wherein an allocation priority of the frequencies in the micro or pico cell base station is such that a primarily allocated frequency of the macro cell has a lowest allocation priority in the micro or pico cell.
In still another aspect of the invention, there is provided a mobile terminal, comprising means for setting up a first uplink connection to a mobile network, means for evaluating at least one property associated with the first uplink connection, and means for deciding upon the at least one property whether one or more second uplink connections can be set up to the network.
In still one aspect of the invention, there is provided a computer program product encoding a computer program of instructions for executing a computer process of allocating frequencies on the uplink of a radio network, the process including allocating a same set of uplink frequencies to be used in two adjacent coverage areas of the network, wherein the set of uplink frequencies is allocated according to a different allocating priority in the two adjacent coverage areas.
The network according to the invention operates on at least two separate frequencies in uplink transmission. In one embodiment, the separate frequencies refer to frequency sub-bands of an MC-WCDMA (Multi-Carrier Wideband Code Division Multiple Access) network. Such a network can employ three separate 5 MHz carriers, for instance. In another embodiment, separate frequencies refer to groups of sub-carriers of a certain frequency band, such as those used in an OFDMA or MC-CDMA system, for instance.
In the mobile network according to the invention, the network comprises at least one base station. Each base station receives uplink transmission in receiving coverage areas. In the invention, there is provided a method and a system of allocating uplink frequencies so that a set of uplink frequencies is reused so that the allocation priority of the set of uplink frequencies is different in the two adjacent coverage areas. In conjunction with the disclosure of the invention, the coverage area can mean a segment of a network that is formed by using a directional transceiver, which is often called as a sector. In some networks, such as in 3G networks, term cell is used for the sector as defined above. In such a context, the coverage area according to the invention thus means a cell.
In the invention, two adjacent sectors, either provided by a single base station or two base stations, utilize the same set of uplink frequencies. For instance, two adjacent coverage areas can use frequency bands F1 and F2. In the first coverage area, the frequency band F1 is a primary frequency band, meaning that an uplink frequency is allocated first to a terminal from band F1. A secondary frequency in the first coverage area is allocated from the frequency band F2. In the second coverage area, the allocation priority is reverse, that is, the primary frequency band is F2 and the secondary frequency band is F1.
By the frequency allocation method and system of the invention, interference in a network is suppressed in a controlled way. At the same time, use of full band and maximum achievable data rates is allowed.
In the following, the invention will be described in greater detail by means of embodiments and with reference to the attached drawings, in which
Mobile terminals have a limited transmission power and, in fact, can employ several carriers or groups of sub-carriers in uplink transmission only close to a base station.
As the figure shows, the power level is high and the mobile could thus also reside far from the base station. When a second carrier f2 is taken into use in addition to the first frequency f1, the mobile's transmission power is evenly divided between the carriers f1 and f2. Correspondingly, when three frequencies f1, f2 and f3 are allocated to the terminal for uplink transmission, the power is equally distributed among them. Thus, it is clear that when several frequencies/carriers are utilized in the mobile terminal, the terminal cannot reside far from the serving base station in view of sufficiency of the transmission power.
In one embodiment of the invention, the network is a UMTS (Universal Mobile Telecommunication System) network applying WCDMA technology. In the following, the structure of the UMTS network is shortly discussed.
The WCDMA can structurally be divided into a core network (CN), a UMTS terrestrial radio access network (UTRAN), and user equipment (UE). The core network and the UTRAN are part of a network infrastructure of the wireless telecommunications system.
The core network includes a serving GPRS support node (SGSN) connected to the UTRAN over an lu PS-interface. The SGSN represents the center point of the packet-switched domain of the core network, and the main task of the SGSN is to transmit/receive packets to/from user equipment that is using the UTRAN. The SGSN may contain subscriber and location information related to the user equipment.
The UTRAN can include at least one radio network subsystem (RNS), each of which includes at least one radio network controller (RNC) and at least one Node B controlled by the RNC. The Node B implements the Uu-radio interface, through which the user equipment may access the network infrastructure.
The user equipment or the mobile terminal may include two parts, that is, mobile equipment and a UMTS subscriber identity module (USIM). The mobile equipment includes radio frequency parts for providing the Uu-interface. The user equipment can further include a digital signal processor, memory, and computer programs for executing computer processes. The user equipment may further include an antenna, a user interface, and a battery. The USIM comprises user-related information and information related to information security, such as an encryption algorithm.
In the example of
In one embodiment, the network according to the invention is an OFDM network. The OFDM network applies a certain frequency band. The frequency band can be divided into frequency sub-carriers.
In an OFDM transmitter, an OFDM waveform can be created from the modulated data by applying IFFT (Inverse Fast Fourier Transform). The principal modulation method used for data modulation can be for instance PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation).
The created waveform contains frequency distributed baseband data corresponding to sub-bands of the OFDM signal. The waveform contains several waves where each wave represents a sub-band signal. The number of waves in the basic waveform depends on parameters given to IFFT transformation. Typically, the waveform consists of 2 to 4 waves but it can also contain more than four waves. Each wave corresponds to a sub-carrier transmitted in the network. Thus, in OFDM, several narrowband carriers are transmitted from the same source in parallel at different frequencies. With regard to the invention, the concept “frequency” can include a group of sub-carriers transmitted on the uplink. Thereby, the groups of sub-carriers applied in adjacent cells are equal to each other but their allocation order is different in the adjacent cells.
As one example of the usage and allocation of network frequencies, we may consider a situation where initially a mobile terminal (MT) is using frequency F1 for speech and data services but desires to launch a high data rate service for which it needs an additional frequency. For that purpose the MT can check the mean transmit power that is used on a primary frequency band. Additionally, if power control is applied, variation of the transmit power is checked. The terminal can then estimate the applied transmit power per an information bit on the primary frequency. Next, the terminal can estimate the required total transmit power if an additional frequency is introduced with a desired data service. A decision is then made in the terminal as to whether or not it can use a secondary frequency. If it is clear that there is not enough transmission power available in the terminal, no secondary frequency is introduced and the desired data service is blocked. If enough transmission power is available, an additional frequency is introduced.
The decision whether or not to introduce an additional frequency can also take into account the coding and modulation alternatives that are available. If link adaptation is applied, the number of applied frequency bands/groups of sub-bands can be selected on the throughput basis. Here throughput is a measure for an error free information rate between a mobile terminal and a base station.
The primary frequency band in the case of cell 400, for instance, is the frequency band that is allocated first to a mobile that resides outside the cell area 402 in the cell 400. If a mobile resides within the cell area 402 and requests additional frequencies in addition to the frequency already allocated from frequency band F1, frequency band F2 is utilized. Consequently, a mobile that resides in or moves into the cell area 404 can first be given uplink frequencies from frequency band F1, then from band F2 and finally from band F3. Respectively, a mobile that is in a sector area 412, is given uplink frequencies primarily from frequency band F2 and secondarily from frequency band F3. Frequency band F1 is not used in the sector area 412. However, when the terminal moves closer to a base station into the cell area 414, frequency band F1 can also be used as a tertiary frequency pool. A terminal residing in a sector 424 obtains uplink frequencies in an allocation order F3, F1 and F2.
In one embodiment, the interference in a radio network can be determined from measurement reports that are received from the mobile terminals using the network. That is, the mobile terminals measure the quality of downlink transmission and send corresponding measurement reports to the serving base stations.
In another embodiment, the network is configured to determine the interference situation in a network from measurement reports that are formed in base stations of the network. For instance, the base stations in the network can convey the measurement reports to a base station controller, which determines frequencies suitable to be applied in the base stations.
In one embodiment, a network is configured to determine the interference situation in the network from measurement reports that are formed in both the mobile terminals using the network and in the base stations of the network.
In still one embodiment, a radio network is configured to determine the interference situation in the network from information obtained from allocation of frequencies in the network. That is, in such a case the interference situation is indirectly utilized in allocation of frequencies. If a certain frequency is rarely allocated in a sector/sub-sector, the network can from this allocation information conclude that the particular frequency is interference-prone in this area and will not allocate that frequency for uplink use.
An interference estimate in a base station can be formed by directly using information measured from uplink, thereby ensuring that the allocated uplink channel is good enough. In addition, the interference situation can be estimated by information that is measured from downlink and signalled to the base station. Measured downlink information indicates the neighbouring cells that the connection interferes with, if the same frequency is put to use. This “two-way check” is to ensure that a newly allocated channel will not cause too much interference for other existing connections in the neighbouring cells. In such a two-way check, also a radio resource situation, e.g. cell load information, from the neighbouring cells can be used for estimating the interference situation between the cells.
The dynamic frequency allocation principle in
In the case of dynamic use of frequencies, the areas where certain frequencies are used may exceed the sector or cell boundaries. In one embodiment, the primary frequencies have a fixed reuse scheme, whereas one or more secondary frequencies can be allocated dynamically. Hence, different mobiles within the same sector can have different FFL's.
The user equipment UE1 comprises means for transmitting 702 an uplink signal on one or more carriers. UE1 also comprises means for receiving 704 a downlink signal. In one embodiment of the invention, user equipment comprises means for estimating 706 the quality of uplink transmission. The estimating means 706 can, according to one embodiment, receive a quality estimate of the uplink in downlink transmission from the network 720. The quality estimate can include information on the receiving power of the uplink signal in a base station, for instance, or alternatively it can include a signal quality value such as signal-to-interference ratio that is measured in the base station. The estimating means 706 can convey the information about signal quality to frequency controlling means 708. The frequency controlling means 708 can, upon the information measured or received by the estimating means 706, decide whether the user equipment could be able to transmit using additional frequencies. In making the decision, the estimating means can perform consideration in view of transmission power, for instance. Then, the estimating means can assess whether the total available transmission power could be divided between the earlier and a possible new uplink resource such that the power level for each resource still exceeds a predetermined power threshold, for instance. A need for additional resources originates from the user's needs. For instance, additional uplink resources may be needed for a temporary need of transmitting a picture file towards another mobile subscriber.
The user equipment UE2 comprises the same functionality as disclosed above in view of UE1. UE2 can reside in the coverage area of the same base station as UE1, but is in a different sector than UE1. Alternatively, the two sets of UE are in the coverage areas of different base stations.
In one embodiment of the invention, frequency-hopping algorithms can be combined with the inventive idea regarding the use of FFL's. Then, the frequencies used in the frequency hopping algorithms can continuously repeat the order of FFL.
In still another embodiment of the invention, one or more logical data flows can be attached to the frequencies in the FFL's. For instance, the user data can be interleaved over all or only some of the frequencies in the FFL.
The invention can be implemented as software in a digital signal processor. Alternatively, the invention can be provided by ASIC (Application Specific Integrated Circuit), by logic components or in some corresponding manner.
It will be obvious to a person skilled in the art that as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
Number | Date | Country | Kind |
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20045368 | Oct 2004 | FI | national |